The Hubble Space Telescope palette (also known as 'HST' or 'SHO' palette) is a popular palette for color renditions of the S-II, Hydrogen-alpha and O-III emission bands. This palette is achieved by loading S-II, Hydrogen-alpha and O-III ("SHO") as red, green and blue respectively. A special "Hubble" preset in the Color module provides a shortcut to color rendition settings that mimic the results from the more limited image processing tools from the 1990s.
A popular bi-color rendition of H-alpha and O-III is to import H-alpha as red and O-III as green as well as blue. A synthetic luminance frame is then created that only gives red and blue (or green instead of blue, but not both!) a weighting according to the two datasets' exposure lengths. The resulting color rendition tends to be close to these bands' manifestation in the visual spectrum with H-alpha a deep red and O-III appearing as a teal green.
Activating the NBAccent module functionality, starts with importing a suitable narrowband dataset via the Compose module.
In this case, when you launch a module that is able to apply a mask, the whole image will flash in green three times.
The Color module is very powerful - offering capabilities surpassing most other software - yet it is simple to use.
This can significantly impact the "correct" (in terms of visual spectrum) colouring of your image.
The two aspects - colour and luminance - of your image are neatly separated thanks to StarTools' signal evolution Tracking engine.
You can convert everything you see to a format you find convenient. Give it a try!