Get rid of Channel Overlay at Curves panel

When you are adjusting colors non-destructively at Curves palette, by default Channel Overlay is turned on with result on Histogram to display curves for all channels. If you want to increase contrast, you can do that, click and drag RGB curve, but if channel overlay confusing you, get rid of it.

Adjust contrast in Curves dialog in Adobe Photoshop

Click on small triangle at upper right corner of Curves palette and choose Curves Display Options..

Click on Curves menu options and choose Curves Display Options

In dialog that opens, uncheck Channel Overlay in Show: section.

Turn off Channel Overlays

That’s it, now you can contretate on contrast without confusing channel overlay.

Curves dialog without Channel Overlay

Note that this change will affect and another Curves dialog from Image menu.

Reference:
Photoshop Help / Adjusting image color and tone
Photoshop Help / Understanding color adjustments

Product used in this tutorial: Adobe Photoshop CS5 Extended