Some faces are a different color

I am still making my tree trunk, I have ‘joined’ a branch and am wondering why 3 of the faces are darker
gray (this is even in orbit view) I just want to make sure I have not changed the properties of the 3 faces
somehow and will come back to bite me later? see pic

Thanks,
R.L. Hamm

Select all the faces and press Ctrl+N, in looks like the faces could be facing the wrong way.

That was it! I built those ones from the back, I had no idea it mattered but I will keep this in mind because it might matter later if I rendered surfaces n such,
Thanks much!
R.L Hamm