Board Thread:Geometry Dash Update Discussion/@comment-27414549-20151212025958/@comment-27413644-20160429142720

Yeah, because RobTop thought there were limited color selections for portals, then he had an idea of using unused colors like white and purple for the gamemode portals. AND that was the result. I mentioned last time that a yellow gamemode portal could be the Swing-Copters gamemode because RobTop mentioned during Update 2.0's development that he might add a gamemode like that in a future update. Since the spider is for 2.1, Update 2.2 will have the gamemode with a yellow portal.