I'm not sure how long this has been going on but there is an issue with the color bulb tile on the dashboard. If a bulb is in CT mode and it is currently off, closing the the color bulb control pop-up via the x in the upper right hand corner immediately turns the bulb back on and turns it to RGB mode using the last color the bulb was set to. Also, if the bulb is in RGB mode and turned off, closing the color control turns the bulb on to the last level it had been previously set to. You cannot close color control if you want to leave the bulb off.
If the bulb is in CT and on, closing the color control windows immediately turns the bulb back to RGB mode at the same level. You can only close via the X if you want the bulb to remain in RGB mode.
This is true of Chrome on Windows (Version 76.0.3809.132 (Official Build) (64-bit) with latest Windows 10) and Chrome on Android (Samsung Galaxy S9 with Chrome 76.0.3809.132 and Android 9) and the Hubitat App (latest beta version). The only way to close out of the color control window is to push the back button to force the dashboard to close. This is happening on Sengled Element Color Plus and Hue RGBW bulbs so it does not appear to be device dependent but a dashboard issue. I can reproduce the problem on every RGBW bulb connected to my Hubitat.