How to customize the car color

My 4 year son loves this game and he wants to play every game with a different car (different color :))

I see the option to change the car color from Garage/Visuals/Paint

There I see a ring with different color gradients and inside it a box gradient colors

I could adjust the color settings only inside the box, which are limited color combination of what is selected in the ring outside.

I am pretty sure I get more color options if i can move the pointer in that ring but don't know how. I keep trying it every weekend to see the settings but I never found. I some times get doubt this can't be done in the pc because I strongly believe that it can be changed something by moving the direction pad or right pad in the xbox controller. But I am not sure how it is done using keyboard in PC.