I am just curious as I notice when the sphero is blinking while it is idling waiting for a connection, it is much brighter than when I set the colour using the setRGB functionality. Am I missing something to adjust the brightness as well. I can't seem to find anything in the documentation.
User3120784, in certain cases when you are using Sphero with the leveling system enabled, this can be seen. I personally just had an issue where the ball would do the brightness discrepancy that you are describing here, and the solution was to just check and then uncheck "Level up" in the advanced settings in the Sphero app.
To address your question in your comment, the difference is that when the Sphero is idling, it is being controlled solely by firmware, whereas the setRGB of the API is using application level code, and telling the firmware to set a brightness, which it may or may not do depending on the "Level up" setting that I mentioned earlier.
How to control LED max brightness using Sphero API