Melt white chocolate (or candy melts) according to package directions. Aim for the minimum amount of time needed to dissolve all solids; stir frequently and briskly to melt pieces without adding additional heat.
Let melted white chocolate cool for a few minutes while completing the next step.
In large mixing bowl, beat softened butter and powdered sugar with a hand mixer on High speed until thoroughly combined and fluffy, about 3 minutes.
Continue to beat on Medium speed while slowing adding melted white chocolate to the butter/sugar mixture. Beat another 3-4 minutes until desired frosting consistency is achieved.
Divide frosting into 4 equal parts. Leave 2 parts in original mixing bowl and transfer 2 remaining parts to 2 separate small mixing bowls.
In one small mixing bowl, add 1 drop AmeriColor Electric Blue gel food coloring and beat on Low speed to combine.
In second small mixing bowl, add 2 drops AmeriColor Electric Purple gel food coloring and beat on Low speed to combine.
In original mixing bowl, add 3-4 drops AmeriColor Electric Lime gel food coloring and beat on Low speed to combine.
You're ready to start frosting!