Hello everyone !
What is the best color space setting in VP50 for laserdisc player ? RGB, 4.2.2, 4.4.4 ?

It works out like this...

RGB is an uncompressed color space that contain separate, lossless data of all three color components (which are red, green and blue).
YCbCr (YPbPr for analogue) 4:2:2 is a color space with lossless luminance (Y) and sub-sampled chroma (CbCr). 4:2:2 means that the resolution for each of the two color components are 66,66% of the luminance resolution (at 1080*1920 it will give you 720*1280 pixels for color).
YCbCr 4:4:4 is the same thing as YCbCr 4:2:2 except that the chroma is sampled as many times as the luminance, giving you full color resolution and is very similar in terms of performance to RGB.

Either way, some consumer sets don't show RGB signals properly unless the monitor/TV is set to PC mode or such. Instead it will down-sample the signal to YCbCr and then make sample it up again for final viewing. I'd try with YCbCr 4:2:2 first. There's very little to gain when Laserdiscs are used. For video game consoles and computers however, always stick with RGB.

thank you for these details !
I will set it to 4.2.2 !
for now I don't see any difference, but I was minding if in movment one was better.