I’m so glad you posted the image. I totally misunderstood your question and got on a tangent about the colour sampler (you clearly said selector – I missed it).
I’ll poke around some more but i still don’t know how we could do that. Have you looked at this plugin? There might be something in there that could work. I’m going to look at it later tonight.
EDIT:
I started playing with this plugin and was able to display the colour selector by holding a single key and then aiming the stylus at the colour selector icon. It’s not exactly what you’re looking for but it’s the next best thing. It will take you a minute to figure out how to use this plugin, though.