It's good you mix it before adding it. That dilutes it to where it's not so concentrated. The marks will look off from the rest of the color. Usually darker or redder than the rest of the body.
The other guy should be alright, he'll be full for a few days and shouldn't need feeding. It's also best to give him some time to clean his digestive tract of anything left over in there as well.
Fish are more hardy than we give them credit for, it's just when they take a injury or get stressed they can quickly collapse from it. When I was working at my local LFS, we had a Betta jump from its jar and was on the floor for who knows how long until I found him that morning. He went in the jar, had some dirt on him and laid there for a while but then he was all better, except a fleck of dirt was on his side.