Board Thread:Geometry Dash Gameplay Discussion/@comment-25769875-20170120122321/@comment-27413644-20170120154022

Here's a more detailed explanation:

1. Select the Color Trigger and place it.

2. Select Edit Object.

3. Click on the (+) button to show "Special Color Select". You can change to BG, G, G2, L, OBJ, and 3DL color triggers from there.