Add sour cream and vanilla and beat until combined.
Spoon 2 teaspoons of filling into 6 small bowls and 1 teaspoon of filling into 1 small bowl.
Color one bowl of filling purple, one blue, one indigo, one green, one yellow, one orange, and one red.
Paint two letters using 6 of the colors and one letter using one of the colors (the bowl with just 1 teaspoon of filling).
Use food use only paint brushes to paint the color into the letter cavities in the silicone mold. Fill the cavity completely so you get nice brightly colored letters.
Freeze the painted mold for 10 minutes.
Remove and pour the remaining cheesecake filling in the mold.
Bake your cheesecake in a water bath for 42-48 minutes.
The top will still jiggle, but look shiny and set.
Remove from oven and set on a cooling rack for 1 hour.
Wrap in plastic wrap and freeze for at least 6 hours.
Remove and peel the mold off the cheesecake.
Set on a serving platter or cake stand.
The cheesecake will take 2-3 hours to thaw at room temperature or it can be refrigerated overnight.