Yellow is another favorite. I've used the same color yellow paint in my last 3 homes. It's sunny and cheerful. We read my new Pete the Cat flannelboard on yellow day.
We also sang a minion song... sang to the tune of Ten Little Indians. One little, two little, three little minions...
I made them by cutting out the shapes from cardstock. They each have a name on the back. The preschoolers absolutely love them. They love to point at their favorite.
The sensory table is filled with yellow rice and squishy schoolbuses.
We have our own rubber ducky pond, complete with yellow water beads to play with. Messy and fun!