As others have said, color can make or break a comic.
I actually started adding gray scale to mine to make the lettering pop off the page a bit more... but know that most likely, my comic will be overlooked for something that IS in color-- as well as art style. It's not manga/anime, so doubly hard to gain notice with some readers.
line work samples

and the gray

i was still working on the bush o the top left...
and the final gray...

... big difference in presentation.
I wanted the comic to be in color, but couldn't really find a vision for it... the color sample below was from a potential colorist with some edits I made. But, you can see that it really does give it that finished look.
lines
final gray
potential color
I know my comic would do better in color, but I am sort of afraid to color it. I like where it is now (in gray scale) though and I'm learning. I actually really like it in gray scale, turned out better than I thought!