Coloring the output makes it slow

[ChrisVilches]

(It's not significant, so it's low priority)

Can be compared like so:

cpdiff -d --color=1 big_file big_file
cpdiff -d --color=0 big_file big_file

My test was a 100000 line file (used the same file for both left and right side).

Average times:
With color: 650ms
Without color: 280ms

I tried changing code inside the coloring library, but it doesn't make it faster at all.
Also, even with --color=1, if I remove the line that applies color, it becomes faster. So the issue is the coloring library (it probably does some checks to ensure it complies with multiple platforms, so that's why I don't want to create my own coloring library). Maybe try using a different one.