One needs to make sure you move both ends by the same amount.  To save fiddling about I have an Action that will do this for me, or you could do it once and then Save... the setting and just Load... it next time.  If you do this in it's own adjustment layer, then you can reduce the Opacity of the layer if the effect is too great.

This change - making the curve steeper - has intensified the Green/Magenta colours.  Nip back two pages and just notice the difference in the red of the flower.

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