Use the HSL/Color tools in the develop module.
I am trying to teach my students how to color correct using the numbers. It is easy in PS, but with lightroom I have told them to move the slider for Yellow and Magenta together to make red and the Green and Blue direction for Cyan. Old Al
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You can also manipulate the red, green and blue curves.
Click on the little curve icon in the bottom right corner of the Tone Curve panel.
Well, that is the hard way to do it in Lightroom, Old Al. Use the HSL / Color tools like I said.