After experimenting, I can conclude that the lights used in Live 2D Mode corresponds to the ‘Band’ or artist playing, examples Poppin’ Party has usual Poppin’ Party colours, Kakumei Dualism (Roselia x Ran) uses Roselia (Blue) and Ran (Red) colours (It’s pretty cool!), Hitori Janain Dakara... well, you can expect what colours are there. But I don’t think CE do just that.
The above is a screenshot of GARUPA PICO and you can see all the vocalist colours as penlights (I mean, I dunno about that orange). But on stage, the colours all represent all the bands. Pink, Red, Teal(?), Blue, Yellow. For TWiNKLE CiRCLE, the band colours are instead the penlights and the song is also under a ‘different band’. Should be the same for Quintuple Smile, I don’t have time to check.
It’s the little details that I love.
Wait, Kasumi's orange... Oh, I feel dumb... Too used to seeing the PoPiPa pink...