Leave the hinges as they are unless you want to completely replace them.

You can paint door hinges, but there is a process. First you take them off. Then you clean them well. Then they can be spray painted with light coats of Rustoleum. After one side is totally dry you can spray the other. It's a lot easier to buy new hinges, if you can find ones that have the exact same measurements as the current ones. If not the same size, they may be difficult to install and have a neat finish. Also replace the strike plates for the latch.

Paint the hinges the same color as the door knobs. I just replaced all of my interior door hardware with venetian bronze hardware and spray painted the hinges the same color.

You will need to clean the hinges, then spray with rustoleum primer, then paint with rustoleum spray paint.

I used old wire hangers and looped it thru one of the holes in the hinge and hung them up. I was able to prime both sides at once and once they dried I was able to spray paint the color.

There's loads of Youtube videos on this as well.

Replace one door knob and see how the silver/ stainless steel looks with the new black door knob. They might look better than you expect. Especially when you factor in the effort to paint them or the expense to replace them. We had horribly over painted hinges and after trying to strip them we decided replacing them was the better option but it yours are clean painting might be worth the effort. Black Sharpie?? LoL

Do you have a RESTORE to fund Habitat near you? I have had great luck finding my exact hinges in their bins, usually at 50 cents a piece. Get a bunch that match your current ones exactly. Spray them with black rustoleum as described previously. Replace one hinge at a time so no need to remove the door. Keep the originals in a bag with all of your silver doorknobs.