Question: I have a scatter chart with a series of numbers in Excel. Most of the time, those numbers are high (>1000). I would like to display the scatter chart with those numbers in the default color, but if the number is < 1000 then display those in red. So essentially I want to highlight just those.

Answer: 
Plot the high and low values from separate columns (or rows):

![Simplified scatter chart with 'highlighting'](https://i.stack.imgur.com/dyLJ4.jpg)
The data point shapes and their colours will probably need to be changed if you want red + another colour and a particular shape but now each 'series' can be selected separately (by clicking on one of the data points from each 'series', in turn) and formatting to suit. I take it that *how* to format (described all over the place) is not a required part of an answer to your question.
For people with the same problems, there is a usefull tool named [FunFun](https://www.funfun.io/1/msaddin), which allows people to use web languages like Html, Css and JavaScript in Excel.

Javascript has a lot of powerful libraries for data visualization, like Charts.js and D3, that you can use with this Excel add-in to create any chart you want.

If you want to test out different libraries, Funfun hosts an online editor with an embedded spreadsheet, where you can see the output of your code instantly.

I made this chart with Chart.js on the FunFun website that I directly loaded in Excel by pasting the link of the funfun online editor below:

<https://www.funfun.io/1/edit/5a32ad9f61242f75d940543f>

Here are some screenshots(Website to Excel Add-in):

[![playground](https://i.stack.imgur.com/2sLv9.png)](https://i.stack.imgur.com/2sLv9.png)

You then load the project in excel with funfun:

[![load](https://i.stack.imgur.com/CcvBH.png)](https://i.stack.imgur.com/CcvBH.png)

[![code](https://i.stack.imgur.com/e9z49.png)](https://i.stack.imgur.com/e9z49.png)

[![final](https://i.stack.imgur.com/EzWDU.png)](https://i.stack.imgur.com/EzWDU.png)