Since you used a fescue mix, I'm thinking that you have more then one variety of fescue grass as there are many.* That would be the reason you are seeing different types of grass and different colors.* This is creeping red fescue and might be in your mix.* Is this what you see?
Here's Chewings fescue.
Here's tall fescue. You can see the red sheaths.
Here's a close up of the blades of tall fescue with a description under the picture.
Here's info on fescues.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.