How did these Eastern Gray Squirrels Get Reddish-Brown Patches?

Actually, I think I saw this before but never gave it any thought. Just now I looked through some old photos. June 2022, to be specific. And I saw a squirrel that I dubbed “Red-faced Grey Squirrel.” I also saw one that I describe as being black or dark grey with yellow patches.

Red-faced Grey Squirrel, June 22 2022

It has the other markings of the one posted above but not the red tail.

Grey/Black & Yellow Squirrel

Actually, now that I’ve got them together, I’m thinking these might be photos of the same squirrel. I did not see this grey and yellow squirrel any other day of the month except June 18. Possibly the background (light above, dark below) made me conclude differently about the colour of the squirrel itself. In the squirrel below, I do not see any yellow in the tail, just as I did not see any red in the tail of the Red-faced Squirrel. In this photo we can’t see the squirrel’s face.