Recently read the simple trick article of color grading technique done with Resolve...
But, wondering if I can do the same thing with available Vegas tools...
I use NewBlue Colorfast to do this on every project. But I would think you could do the same with the Secondary Color Corrector in Vegas. In the "Limits" tabs at the bottom try setting the width of the Hue control to max, leave the Saturation limit at default, the use the Luminance limit controls to select just the darkest areas (I usually use 25IRE in Colorfast) and use the smooth control to feather the effect. Then use the Secondary CC saturation control to desaturate to taste.
ah yes...
Just tried it..., NewBlueFX ColorFast is really giving an instant solution... but having to do 'manual' with Color Corrector secondary, at least giving you a more understanding how it works...
The small trick really does giving a lot of differences.