Answers.Body: <p>I believe the main reason is so that the pieces are easy to identify in the instructions - as many LEGO sets don't have the Technic style "List of elements used in this step" it's always a fun game of "Spot the difference" to see what's changed:</p>
  
  <p><img src="https://i.sstatic.net/FB4EX.png" alt="Multi-coloured interior"></p>
  
  <p>If those pieces were all red, then the target audience (5+ on those sets for example) might find it very frustrating to build.</p>
  
  <p>(Even with the list of elements to use in a step it can often be quite an effort to find where a particular part goes.)</p>
  
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Answers.Text: One thing I've noticed is that many models go one step further: not only are certain parts in unrelated colours, but sometimes all the parts of that size/shape are the same colour, making it easier to find the part in the pile of unused parts.
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Answers.Text: its interesting that even on the BTTF and Ghostbusters that do have the parts list that they still do that - the BTTF wheel catchers were both red and blue.
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Answers.Text: @Mr.ShinyandNew安宇 That's probably so they minimize the number of unique parts in a set. I've noticed they'll occasionally combine smaller bricks to make a single instance of a larger brick a few times per set for this reason (I assume) as well.
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Answers.Text: @Feathercrown yes. There are several competing factors at play regarding the cost of parts, and sets are always trading off certain things against cost. The precise calculations are secret, but also, sometimes cost isn't the deciding factor, such as in certain sets where they specifically throw in extra of certain elements so that they can give fans more of them. An example is the 1x3 dark green tile, [which Jamie Berrard (the designer) explained was abundant in the Sopwith Camel set so that fans could have lots of them to use afterward](https://youtu.be/8e9EmCobfos).
Answers.UserDisplayName: Mr. Shiny and New 安宇
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Answers.Body: <p>One reason is ease of identification, even in sets not intended for the youngest age range.</p>
  
  <p>For example in the Millennium Falcon 7000-piece "mega set" all the 1x16 Technic beams are dark grey, the 1x14 are black, and the 1x12 are light grey. There are about 70 of these beams in total. Almost all of them are invisible in the final model since their main purpose is to give the model its structural strength, but it's an easy way to sort them. There is a similar color coding for the longest "1 x whatever" bricks, as well.</p>
  
  <p>In the same model, the half-built structural frame is almost symmetrical end-to-end, the sides are mirror images, and it is almost identical when turned upside down, but a small number of coloured parts make it easy to orient it correctly and avoid discovering a mistake after many building steps.</p>
  
  <p>Some color coding seems almost universal across sets - for example black and blue Technic connector pins. Again, an easy way to avoid mix-ups when building.</p>
  
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Answers.Text: Indeed - the pins were a long-running colour convention - it used to be black and grey (friction and non-friction), but even those are available in a number of different colour combinations these days!
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Answers.UserDisplayName: alephzero
Body: <p>With recent and current sets, I noticed that some contain parts of a totally different colour than the rest of the set. An example is <em><a href="https://brickset.com/sets/8200-1/Radiator-Springs-Lightning-McQueen" rel="nofollow noreferrer">8200-1: Radiator Springs Lightning McQueen</a></em>, which contains a blue 2×6 plate, 3 yellow 1×2 plates, 2 white 1×2/1×4 angle plates, and 2 grey 1×4 plates, while Lightning McQueen is red. </p>
  
  <p>Parts like these aren't usually <a href="https://www.lego.com/biassets/bi/4639846.pdf" rel="nofollow noreferrer">visible in the finished model</a>.</p>
  
  <p>Why are they used?</p>
  
  <p>These are parts that should be available in most colours, including red. Did they have an overstock in these colours? Is it to make for easier building? Since this way both the model and the instructions aren't a big blob of red? </p>
  
Tags: <sets><colour><piece-information>
Title: Why do some sets contain parts of an unrelated colour that are hidden on the final model?
UserDisplayName: SQB
ThreadText: # Why do some sets contain parts of an unrelated colour that are hidden on the final model?
  
  (Asked by: username_0 on 2014-02-24)
  
  With recent and current sets, I noticed that some contain parts of a totally different colour than the rest of the set. An example is *[8200-1: Radiator Springs Lightning McQueen](https://brickset.com/sets/8200-1/Radiator-Springs-Lightning-McQueen)*, which contains a blue 2×6 plate, 3 yellow 1×2 plates, 2 username_3 1×2/1×4 angle plates, and 2 grey 1×4 plates, while Lightning McQueen is red.
  
  Parts like these aren't usually [visible in the finished model](https://www.lego.com/biassets/bi/4639846.pdf).
  
  Why are they used?
  
  These are parts that should be available in most colours, including red. Did they have an overstock in these colours? Is it to make for easier building? Since this way both the model and the instructions aren't a big blob of red?
  
  **Tags:** sets, colour, piece-information
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2014-02-24. Score: 23
  
  I believe the main reason is so that the pieces are easy to identify in the instructions - as many LEGO sets don't have the Technic style "List of elements used in this step" it's always a fun game of "Spot the difference" to see what's changed:
  
  ![Multi-coloured interior](https://i.sstatic.net/FB4EX.png)
  
  If those pieces were all red, then the target audience (5+ on those sets for example) might find it very frustrating to build.
  
  (Even with the list of elements to use in a step it can often be quite an effort to find where a particular part goes.)
  
  > **Comments:**
  > **username_2**: One thing I've noticed is that many models go one step further: not only are certain parts in unrelated colours, but sometimes all the parts of that size/shape are the same colour, making it easier to find the part in the pile of unused parts.  
  > **username_3**: its interesting that even on the BTTF and Ghostbusters that do have the parts list that they still do that - the BTTF wheel catchers were both red and blue.  
  > **username_4**: @username_2 That's probably so they minimize the number of unique parts in a set. I've noticed they'll occasionally combine smaller bricks to make a single instance of a larger brick a few times per set for this reason (I assume) as well.  
  > **username_2**: @username_4 yes. There are several competing factors at play regarding the cost of parts, and sets are always trading off certain things against cost. The precise calculations are secret, but also, sometimes cost isn't the deciding factor, such as in certain sets where they specifically throw in extra of certain elements so that they can give fans more of them. An example is the 1x3 dark green tile, [which Jamie Berrard (the designer) explained was abundant in the Sopwith Camel set so that fans could have lots of them to use afterward](https://youtu.be/8e9EmCobfos).  
  
  ---
  
  ### Answer by username_5 on 2020-04-20. Score: 4
  
  One reason is ease of identification, even in sets not intended for the youngest age range.
  
  For example in the Millennium Falcon 7000-piece "mega set" all the 1x16 Technic beams are dark grey, the 1x14 are black, and the 1x12 are light grey. There are about 70 of these beams in total. Almost all of them are invisible in the final model since their main purpose is to give the model its structural strength, but it's an easy way to sort them. There is a similar color coding for the longest "1 x whatever" bricks, as well.
  
  In the same model, the half-built structural frame is almost symmetrical end-to-end, the sides are mirror images, and it is almost identical when turned upside down, but a small number of coloured parts make it easy to orient it correctly and avoid discovering a mistake after many building steps.
  
  Some color coding seems almost universal across sets - for example black and blue Technic connector pins. Again, an easy way to avoid mix-ups when building.
  
  > **Comments:**
  > **username_1**: Indeed - the pins were a long-running colour convention - it used to be black and grey (friction and non-friction), but even those are available in a number of different colour combinations these days!  
  
  ---
  
  