How to paint over glass uneven mosaic tile?

I would make sure it was stripped completely clean and was completely bone dry. Then use a coat of something like Kilz or another primer as a base. From there, with the dark green marble, I'd paint this tile a very pale compatible green. By compatible green I am talking about a green that is of the same color family, but VERY PALE - almost white.

Then the cabinets - if they don't need to be black, The same green you used on the tiles could be used. It would give the kitchen a country feel, with the green, but would brighten it immensely. Geeze! Black cabinets with the dark green marble just sounds gruesome.

Maybe some fancy fairy/Christmas lights twined with fake vines around/thru/patterned on ceiling !?

I would not paint the glass tile. I would check to see if the grout could be lightened, perhaps with a subtle green to compliment the counter tops. Sand and paint the cabinets cream on the inside and the same subtle green on the outside. Remove some of the cabinet doors on the top cabinets and either replace the panels with glass or leave them off. Change the hardware to something bright. Also you can add under cabinet and inside cabinet lighting. I love the counters by the way, they should be the focus. Pendant lights with crystal or light cream shades.

Look into something like smart tiles. There are less expensive versions out now. They are peel and stick, easy to cut and flexible sheets that look just like tile. Super easy to use, come in many colors ad shapes. Here's a link to some of what they have at Home Depot: https://www.homedepot.com/b/Decor-Wall-Decor-Peel-and-Stick-Backsplash/N-5yc1vZcksp?NCNI-5&searchRedirect=peel+and+stick+backsplash&semanticToken=20082000+++%3E++++st%3A%7Bpeel+and+stick+backsplash%7D%3Ast++cn%3A%7B0%3A0%7D++cn%3A%7B0%3A0%7D++peel+and+stick+backsplash+%7Bcategory%7D+qu%3A%7Bpeel+and+stick+backsplash%7D

You can change the grout color with Maepi Grout Refresh. Comes in many colors, check Amazon.