In the bowl of an electric mixer, cream together butter and confectioners sugar until light and fluffy. Start on a low speed and slowly increase it to high.
Add in peanut butter and beat until incorporated.
Drizzle in the vanilla and then the heavy cream. Mix on low until combined and then turn speed up to high and beat for 5 minutes, or until light and fluffy.
Add food coloring until the color almost resembles peanut butter. It should be a little lighter in color.
Notes
Food coloring will continue to darken over time, so stop adding gel when the buttercream is a little lighter than the desired color.
All ingredients should be at room temperature for best results. Mixing ingredients of different temperatures can cause the frosting to break, resulting in a buttercream that is separated.