This puzzle deals with color channels. It is similar to Simon Sends in that it uses additive color mixing, but it has a fourth “brightness” channel in addition to the typical red, green and blue. This 4-channel color system was used in text mode on computers running DOS in the 1990s.
Separating the color channels yields a set of letters and symbols to be read vertically:
The symbols can be decoded as Emoji Math, yielding the clue phrase UNICODE 9660. The name of the referenced Unicode character is the solution.
BLACK DOWN-POINTING TRIANGLE