SelectedColor on binding should be defined as TwoWay

[PLFJY]

I used this control today, but I found the default binding mode of SelectedColor is OneWay. So I must assign it for Mode=TwoWay manually everytime. I think it can be set as TwoWay binding mode in default, which can simplify some unnecessary duplicated code. I'm willing to contribute code for this and open a pull request for this