Yes, I did note the change in color tint, but I didn't keep track of the how or why, but it did occur after I added the shadow catcher. The HDRI I used is a winter scene without a visible sun. It would make sense that the overall tone of the scene would be bluish, or a high Kelvin temperature range.

Hopefully, this will solve your issue and show you where to address it. It helps to know your way around the material room where Cycles is concerned. I would like to see your results.