Cover Letter Length

How important is the length of cover letters? Will recruiters turn away from longer ones and give it no chance? Also, does adding color to a black & white resume improve it or make it stand out more?

I don't see cover letters as necessary, but nothing wrong if you want to make one.

For your cover letter, the shorter the better. I mean that to the extreme. 1-3 sentences would be great. I've seen plenty that short and I'm more likely to read that than the single-spaced full page manifesto I get.

In my experience, the longer the cover letter, the weirder they get.

I like seeing a little color in resumes. I often advise people to use Maroon on the headings of their resume.