If you want to paint above it, you'd have to remove the piece of wood up there, being careful not to damage the cabinetry. However, it would look better to get a side panel that matches your cabinetry and bring it all the way down to the counter on that entire side wall (including the narrow rectangular area under the cabinets) so that the wall oven cabinetry looks built-in/completed; if you paint that side wall the oven cabinetry will look disjointed.

Can you paint it? Maybe. Should you pain it? No. That surface really should never have been tiled either, it should have been the veneered end panel it was installed to be. Your gc can easily replace this, it’s not like the material is hard to find.

Thank you for the responses. I didn't think that the wood on the cabinets could be matched with veneer. Way back when the house was built, they matched, but the cabinets and the laminate (or whatever it is) aged differently colorwise.

The cabinet trim is on top of the area in question so I wonder if that could be removed then put back over the veneer?? I don't think just butting the veneer right next to the trim would look "clean."

"Way back when the house was built, they matched, but the cabinets and the laminate (or whatever it is) aged differently colorwise."

Do you have a local cabinet maker who can match it for you?

You asked what should be done.

Now you’re asking about how it should be done. Discuss this with your GC. Let him know you want a better color match (whether in wood veneer or laminate - although you may as well go with veneered plywood - you can finish it to match). It’s just not that hard to fix.