Simply read the former posts, 2 ways to remove just „color sand“ are described for denoise (profiled) module (one with non local means, and one using wavelet denoise)
You can save the settings as presets.
I think the color smoothing options in the demosaicing module also reduce color noise.
Have you tried the old lowpass module, something like:
I’ve to admit I usually like the result.
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A display refered denoising would come too late in the pipe (the data would not be linear anymore, which would be problematic as we do a lot of averages when denoising, so better have linear data).
A sensor denoising using all channels together is fine (like non local means for instance: the 3 channels are used to compute the distance between 2 patchs, and are denoised together).
Denoising each channel independently from the others can give ugly color noise sometimes, if the denoising methods works only channel per channel, then it is nice to do a transform to Y0U0V0 that tries to concentrate all the redundant information of the RGB in the Y0 channel and all the noise in the U0 and V0 channels:
Y0 = (R+G+B)/3 (assuming identical noise variance on the RGB channels this reduces the noise variance by 3 – in darktable we adapt these coefficients to white balance multipliers)
U0 = 0.5 * R - 0.5 * B (try to cancel the signal to keep only the noise)
V0 = 0.25 * R - 0.5 * G + 0.25 * B (try to cancel the signal to keep only the noise)
This then makes it possible to denoise much more aggressively U0 and V0
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Thanks. Tried this, also tried below @phweyland’s advice. First works better with my Panasonic, latter with friend’s Cannon 
Saving presets for particular module and adding such module with settings to image with two clicks, done better than I could expect.
Using lowpass for noise reduction is a neat trick! First time I saw it. Thank you for the tip!
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One looks like too much grain or artifacts under physical zoom…chroma is often green /blue artifact that can be clumped or finer in nature…often you will see luma noise in a sky and chroma in shadows…this is way over simplified but you asked about how to recognize it now what it is…so hopefully this helps…@rawfiner has excellent videos…watch them on youtube and you will be the noise master…
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maybe a preset would be handy?
Good idea 
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