If you create a project in 4.17 and follow the Repro steps, you will be able to adjust the colors of individual lens flares. If you copy the 4.17 project into 4.18, 4.19, 4.20 Preview, or 4.21 the feature will work. It will NOT work if you create a new level in any editor version after 4.17 (instead of copying the project), therefore I am marking this as a regression.
Result: You can no longer change the colors of the individual lens flares like you could in 4.17. See attached screenshots.
Head over to the existingAnswerHub thread and let us know what's up.