Rigot mortis begins to set in at 3 hours...and goes away roughly 3 days later.

I don't know about the redness, but I know when my dad died he died at my oldest sisters & my middle sister went in around 8 a.m. To check on him & then around 9 a.m. & in that hour he passed away. Anyway, when we tried to get him from the bed to the livingroom floor he was already cold & a little stiff.

Now I can't say my answer is 100% correct, but here is what I have been taught. First, the body takes up to 2 hours to begin Rigor Mortis. That is from a chemical job of the muscles, they harden and the body becomes very stiff. What I have been told in the past is that it hits it's peak of Rigor mortis at approximately 12 hours, then reverses and is done around 24-48 hours. However, the class I'm in now states it can last a few days.
Discolouration of the skin comes from Livor mortis. That is from a dead body lying down and the part of the body that is lowest turns colour due to gravity. The blood and weight of organs causes this, the skin can turn red, purple, and maybe green and blue.
I hope this helps, but like I said, I'm not exactly 100% correct on it.