My kids already know their colours but that doesn't stop us from loving games that are based around particular colours. You don't need to be learning colours to set up these activities.
Here is one example of when we did a YELLOW EXPERIENCE.
I just used an under bed storage container and filled with warm water and yellow food colouring.
I collected a bunch of yellow materials that I had in my arts and craft collection. Then used the yellow number mats for padding around the edge for the kids to kneel on.
The next day, we followed on with this activity by adding the above materials to their bath with a few drops of yellow food colouring again.