I just found a small bug in RGBA color selector UI (property is a float array whose length==4) : when Alpha==1, you can disable the ui using something like col.enabled = False in python, and it shows the difference. but when Alpha==0 there's no visual difference on the ui when disabled/enabled. they look the same. (The ui is disabled from operation, so no problem there, just the appearance didn't change) Set alpha between 0-1 affects the appearance also. E.g. set Alpha==0.3 and disable the ui, there's only a tiny difference in the looking.
I tried this in Blender2.8's branch. But seems not working properly in 2.79 either. I know there's a rare case that we absolutely need 4 value color picker but it would be great to get it fixed. thanks!