Adjusting saturation of individual color channels?

Question

In Photoshop, the Hue/Saturation adjustment allows individual adjustment to each color channel. So for instance, one can lower the saturation of only red, without affecting global saturation. I've used it thousands of times over the years, especially when shooting with Nikon cameras, which often seem to have artificially over-saturated yellows, or when shooting HDR, which tends to boost reds.
I've been scouring the internet for a plugin (or a hidden slider) to do the same within FCPX, to no avail. I'd love to be able to adjust a clip's global saturation up, while specifically lowering saturation in reds and yellows. Or at times, a clip simply has an oversaturated color that I want to diminish.
I've thought about using selective masks to grab a hue and desaturate, but that's a weird workaround to me.
This is a chance for the haters and maligners of FCPX's color correction to make themselves heard. Any thoughts?

Answer 1

Try this and see if it helps:
http://sight-creations.com/fxexchange/ChannelSaturation.zip
(if you need intallation help: http://sight-creations.com/install4fcpx/)
This is the parameter arrangement:
The Value parameters can be used to darken/lghten the channel.  I also added  "overall" Brightness and Contrast controls (if you darken or lighten too much with the values.)  The Pivot is part of Contrast and is a midpoint of sorts (it more or less is a fine-tuner for contrast.)
Big hint: small moves. Also, once you desaturate a channel, you'll probably want to increase it's Value (and vice versa) to help balance the other channels so that you don't develop an unwanted cast. You can toggle the original state with the effect by clicking on the blue square dot by the effect's name in the inspector.
Here's a little *extreme* before/after:
(untouched original and probably not the best example [but I have problems with oversaturated reds as well.])
(after extreme desaturation of reds, some additional brightness and a little contrast along with the value adjustments — there's a fair amount of latitude with this effect.)
HTH