Avisynth, Change Chroma not Luma

[lolman]

How to change Chroma levels of a video, without changing Luma.... and vice versa using Avisynth?

Ex:
I wan to use
Levels(56,1,200,0,255)

It changes both chroma and luma I think.

Is there a way to change Chroma only?
Or change Luma only?

[Skiller]

MergeLuma( Levels(56,1,200,0,255), last ) #affect Chroma only
MergeChroma( Levels(56,1,200,0,255), last ) #affect Luma only

[poisondeathray]

or ylevels

http://avisynth.nl/index.php/Ylevels

[jagabo]

ColorYUV(gain_y=x, off_y=y, cont_y=z)

[lolman]

Thanks Guys