I've finished quite a few Yoda's in my time and I can say with some certainty that there is no definitive Yoda colour.
The puppets from the OT and PT differ considerably in color tone, even some of the original ESB and ROTJ puppets are painted a little differently. Also factor in lighting and so forth, the puppets look different in various scenes so screen grabs cannot be relied upon as a true 'swatch' on paint colour.
The method that I have always used is solid very pale green basecoat, then various washes of green, yellow and light brown through an airbush until I find a colour which doesn't displease me too much.
It's not an exact science and there is NO single colour solution.
One tip I can offer is, the green tone is lighter than most people imagine, don't opt for a rich dark green basecoat because it will look terrible. Start very light/pale green, handmixed, then darken down to your satisfaction with the various subsequent paint layers on top.