I think I have found an issue with the color of the bulb displayed on a dashboard tile using the Color Bulb template.
Initially and before changing any of the Color Bulb Options, the color of the light bulb icon's background is white. Once a Color is picked from the "Color Bulb options" section, the background of the bulb icon changes to the selected color. The icon background remains that color even if the bulb is changed back to a Color Temperature, instead of a RGB value.
I found this initially with tiles for color bulbs and also tiles for groups of color bulbs. I was able to reproduce this with a Virtual Color Bulb. The only difference with this last test is that the Virtual Bulb starts off at a color by default, so it can apparently never go back to the white icon background.
The following screenshot shows the virtual color bulb called "Test Dashboard Tile", a Group containing the two lights to the right called "Solarium Reading Light" and the two lights contained within that group.
This test was done using Hubitat Version 188.8.131.52, Google Chrome Version 79.0.3945.130 (Official Build) (64-bit) on Windows 10 version 1903, OS Build 18362.592.