An infected wound can look not just red, but like a giant bruise. Black, purple, with a little red in it and when you touch it, it will hurt a lot or burn. It does swell than normal and there might be yellow pus coming from the wound. You need to either go to a hospital or see your doctor, because the infected wound can make you very ill, and infections can be fatal if they're not treated right away.
You can also use 3% Hydrogen Preoxide on the wound, because it's for infections and more. Just don't put it inside of the wound if it's real deep, because it'll start eating away everything inside.
An infected wound will look very red warm and blanch to touch. It always has swelling than normal and there may be pus or foul smelling drainage coming from the wound. You should contact your physician if you have such wound.