The Filter module allows for the modification of features in the image by their colour by simply clicking on them. It's as close to a post-capture colour filter wheel as you can get.
Filter can be used to bring out detail of a specific colour (such as faint Ha, Hb, OIII or S2 details), remove artefacts (such as halos, chromatic aberration) or isolate specific features. It functions as an interactive colour filter.
The Filter module is the result of the observation that many interesting features and objects in outer space have distinct colors, owing to their chemical make up and associated emission lines. Thanks to the Color Constancy feature in the Color module, colours still tend to correlate well to the original emission lines and features, despite any wideband RGB filtering and compositing. The Filter module was written to capitalise on this observation and allow for intuitive detail enhancement by simply clicking different parts of the image with a specific colour.
"L, RGB" simply uses the loaded luminance dataset for luminance and uses red, green and blue for the color information.
Worry not; subsequent processing in StarTools will remove the color bias, while restoring and bringing out detail.
The classic Denoise module caters to the former, while the Denoise 2 module caters to latter.
Uniquely, thanks to the signal evolution Tracking engine, this color calibration is preferably performed towards the end of your processing workflow.
This can significantly impact the "correct" (in terms of visual spectrum) colouring of your image.
You can convert everything you see to a format you find convenient. Give it a try!