Why is my Burn Scar a Brown/purple Colour?

About 4 months ago I stepped on a hot marshmallow roaster and burnt my foot (somehow top and bottom-bottom wasn't bad) to what my dad said would have been a 2nd degree burn and it has a little raise to the scar, it is just a really weird brown/purple colour that gets really dark when it seems to get warm and lighter as it gets cooler and I was wondering how long should it stay this way, like forever, a few more months or is their no way to tell and if this is normal?