Im having trouble finding quests my level since I moved to Velen, am I always supposed to do quests above my level?
Or does green mean "try it"
You can do anything in green technically as that means in range. In theory you could even do reds but you shouldn't because it gives you stuff often you won't be able to use and its tedious fighting a red monster and it destroys the durability of your weapons.
What I can tell is that you can just explore a bit and you will start finding stuff around your level. And do any sidequests or contracts you have first. It tends to lump near level stuff together although you will also find stuff above your level. Don't be afraid to explore and come across stuff over your level. Just run away from it. Its generally hard to die unless you just start running up to everything and start immediately fighting it. There are honestly probably way over 100 hundred things you can do between monster nests, random subquests, guarded treasures, caves, etc. that are level appropriate. You just have to explore around a bit.
Also remember you can go back to White Orchard to mop up any of the stuff that was over your level the first time you were there.
I thought the same thing the first time I went to Velen but just by kind of looking around and mixing in the main quests/sub quests I realized there is actually a ton of lower level content there. You just have to look for it. And just because you find a high level thing, it doesn't mean that there also isn't low level stuff around. It mixes in the high and low all over the place unlike other games where its all grouped within a small range.