I noticed that the colour of a Colour Card can be changed only if there are no keyframes. That is, only if it’s new Colour Card and you are changing its colour for the first time.
The moment you add a keyframe the Colour Card refuses to accept the choice from the Picker and you are obliged to go the normal way, using the RGB sliders or typing values in Data View.
The problem with RGB sliders is that you are modifying one parameter at a time and getting partial colour results in the process. It can be confusing, and seems to me unnecessarily dodgy.
The Colour Picker instead shows you the change immediately, it is a much better judging tool.
For time’s and simplicity’s sake, one should be able to choose intuitively, exactly the same way as when creating palette colours.
I think this option should be added.