I think you will end up with big problems. After the vinyl ages and roughens, you could probably paint them, but not when new, plus you're defeating the entire purpose of these being "maintenance free" and never requiring painting as wood windows do. It's too bad you didn't specify these in the contract. I assume this builder buys thousands of windows from the manufacturer at a good price, and if they are special ordered in black, he will pay more.

You will have to re-stucco the house with new construction windows.

What a beautiful charmer! You must be having so much fun playing dress up with this gorgeous house! I think you made a solid choice with the black windows and they look great. I'm marinating on the how we can brighten up that amazing front porch...so stay tuned for more on that. I dont think painting the stone is completely off the table. I would obviously only do the exterior siding and leave foundational stone natural like it is. I think painting might brighten it up a bit and plus I love the uneven texture that comes out once its painted. On your two windows that pop out on front and side of house, if budget permits, a copper roof might be fun?

I have found the visualizers great for figuring out what color I like. As with any web based or computer coloring tool, what you see isn't always what you get when you actually buy a bucket of paint and put it on your walls. It should get you close, but there is always some manual tweaking that has to be done to get the color to look the same in person as on screen. It isn't that the computer screen is wrong, it just doesn't account for any lighting changes from what they originally set up, and in real life, lighting changes throughout the day and is different indoors from outdoors and and and.. . . Please make large samples and try them before investing in a gallon of paint.