So I sat down this morning to recreate this for a report, and discovered that I couldn’t repeat the steps.
It appears that Light Function materials do read seperate channels (as Emission inputs) ok - you still need three Lights & three materials however.
Apologies for any confusion!
Three Light Function materials & Lights + 1 RGB texture.
Tip: Set your Lights to extremely high intensities, and tweak their Indirect Lighting Intensity to get nice HDR glows and GI bounce from them (this is at 8000000.0 & 0.3 ILI per light), and seperate (or rotate) the lights very slightly for chromatic aberration:
