Some redness is part of healing. The question is which kind, and the difference is not about shade but about direction of travel.
As a wound heals, once the scab forms and the immune system begins protecting the wound, the wound becomes slightly swollen, red or pink, and tender. This stage takes about 2 to 5 days. So early redness has a place in the normal sequence, and a window.
A healthy wound bed is also red or pink. After a debridement, the area will be red or pink in color and look like fresh meat — and wounds that are pale, purple, or black are less likely to heal. Red, in the wound itself, is the color you want.
On the other hand, every list of infection signs includes redness, and always in terms of change. More redness. Worsening redness. Redness and tenderness around the sore. Redness, increased warmth, or swelling around the wound.
More, and worsening. Not redness, but redness that is increasing.
And one kind of redness is spreading rather than just increasing. With cellulitis, skin redness or inflammation gets bigger as the infection spreads, and a skin sore or rash starts suddenly and grows quickly in the first 24 hours. Clinicians may mark the edge of the redness with a pen to see whether it goes past that border over the next several days.
There’s no set measure for how much redness is acceptable, or how far from a wound it may extend.
The practical substitute is a comparison you can actually make. A photograph today gives you something to hold tomorrow’s redness against, which is more reliable than memory.