I love color (in other people's homes), but it is hard to imagine... Is Grape the color you are looking at on a sofa for sale, or is it some version of purple that you really like? What color is grape, anyway?

I don't think I would care for a grape sofa in your space. I like the idea of your blues, and you have the red-toned furniture, and then a paler yellow background.... maybe just stick with your blues and paler background so that things can harmonize around a tighter theme.

Specifically, I would choose a very neutral sofa, and then accessorize with some blue pillows, with maybe a hint of paler yellow in some of them.

I’d go with a neutral sofa and (if I wanted to bring grape into the mix) grape accessories/ pillows/ etc. But I’m not a fan of large amounts of vibrant color, it puts me on edge.
But...it’s your house, and if it brings you joy, go for it!