UPDATE FROM MABULA
I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred  after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Â Before I release it, I will make sure that everything is working properly and then I will release it.
When I use the RGB Combine tool, for LRGB its treats L as a white layer of 4 layers, forcing the result to white. This is not correct. L is the intensity to which you take the RGB intensity, ... you compute the amount R contributes (say 23%) to a particular pixel, then multiply that times the L amount to get the new intensity for R, etc. Each color is painted onto L proportionately.  The results should not be White but boosted colors, based on their proportion to each other multiplied by the Luminance level, give it an even strong intensity than it would have had without the L. Its completely not working as is, since its treating a 4 (LRGB) as equal layers.  For example let's say your Luminance is 200 for a pixel, and you compute the RGB (based on RGB not LRGB) percentages for that pixel based on your data, let say that comes 37%/44%/19% (you throw away the old RGB intensity from the individual files and replace it with the intensity you compute here), so then you would end up with 200x.37 = 74 RED, 200x .44 = 88 GREEN, and 200 x .19 = 38 BLUE.  Instead you're just giving us white.  Its not about moving the slider down so white is not there revealing the color its about recomputing the intensity of each pixel based on L values as percentage of RGB, its a new intensity. Â
For example, here is APP on the LEFT;  and ASIStudio on RIGHT (same FITS files as input). Yes I pushed recalc after selecting files on APP using LRGB formula.Â
Skye (@skysong)
I believe you are right about this. I tend not to notice the issue as I typically process luminance separately and combine it in Gimp as the last step. Now that I think about it I am a bit surprised it hasn't been raised more often.
JC
@connor231 Oh I'm a GIMP user too, how do you do your technique? They fact that we get white/ gray with LRGB, then reduce L to low levels (basically to remove it back to RGB) proves the current algorithm is not working. The color should be "boosted" by the L proportionately, but instead L is added in as white layer, which is wrong.
Skye (@skysong)
If you are asking about the final combination step - its fairly straightforward.
You load the mono luminance and the rgb image into Gimp as separate images. Copy the luminance, switch to the rgb image and select 'Paste as' 'New Layer in Place'. The layer panel will now show two layers. Select the top one (your mono luminance) and change the layer blend mode from 'Normal' to 'Luminance'.
At this stage you can play with the Opacity of the top layer. You can leave it at 100%, but I sometimes find that reducing it to about 70% can look a bit better. Once you have chosen the opacity, then select the luminance layer and do 'Merge Down' (either in the Layer menu or by right clicking the layer entry) to create a normal flat image.
Lastly, I still find that the saturation sometimes takes a minor hit and I give it a saturation boost.
This is just how I like to do it. There are other methods - some people prefer to switch to LAB colour, swap the luminance, and switch back to rgb.
JC
Skye (@skysong)
If you are asking about the final combination step - its fairly straightforward.
You load the mono luminance and the rgb image into Gimp as separate images. Copy the luminance, switch to the rgb image and select 'Paste as' 'New Layer in Place'. The layer panel will now show two layers. Select the top one (your mono luminance) and change the layer blend mode from 'Normal' to 'Luminance'.
At this stage you can play with the Opacity of the top layer. You can leave it at 100%, but I sometimes find that reducing it to about 70% can look a bit better. Once you have chosen the opacity, then select the luminance layer and do 'Merge Down' (either in the Layer menu or by right clicking the layer entry) to create a normal flat image.
Lastly, I still find that the saturation sometimes takes a minor hit and I give it a saturation boost.
This is just how I like to do it. There are other methods - some people prefer to switch to LAB colour, swap the luminance, and switch back to rgb.
JC
Yeah i saw there is a way to load all 3 colors separately to GIMP, and then the L, as the last layer and flip it to Luminance, but its I'll have to spend some time to learn it. This is probably the best way to to do it in GIMP, but I takes some time to learn it.  Would be even better if APP can update their algorithm.Â
Skye (@skysong)
I didn't suggest loading r, g and b separately to gimp. Just load the rgb combined file (not lrgb) and the mono luminance. Then it can literally be about four clicks and you are done.
JC
Hi Skye @skysong,
When you apply a luminance layer 100% it can seam that the image is whitened. But if you simply enable saturation and/or increase saturation in the preview filter, the colors will be there. Our RGB combine tool works currently with the HSL color model and L is a real L, not a white layer.
I have opened a new issue on my todo list to have a good look at the Luminance calculations to make the RGB composites in the RGB Combine Tool.
I know that this whitening effect is there, so I will definitely try to have this work better going forward 
It is on our todo list, to improve this with a more advanced color model going forward.
Please let me know if this helps,
Mabula
