How to make a color selector?

I am creating a material that has a base texture map.
I am adding a color multiply, so I can change the color of the texture map.

How can I do that, that I am having a color picker inside of my Material Instance?
When ever I want to change the color, I just want to pick it inside of my material instance.

See screenshots attached.

thank you so much for any little help,
appreciate it!