Cleaning blood stains on jeans

I tried using Hydrogen Peroxide 6% on a blood stain on my white and black jeans. It cleared the stain from my white jeans but the color on my grey jeans has turned black where I used it. (it was just a patch test, dw). However, how do u use Hydrogen Peroxide to remove stains so it doesn't damage or bleach ur clothes. I have no idea how to use it and I'm scared I'll ruin my new jeans. 😭 What if I rinse the jeans immediately with cold water with soap after using hydrogen peroxide?