The people behind ToonBoom was also the people who made the traditional animation testing and coloring tool. Went to there site, it looks like they got a line test tool. I think the people/company behind ToonBoom was the one who also made the traditional line test tool and coloring tool for the industry. So I guess they will be a good choice.
I am making a small short, and I am using Photoshop to color every image. But I guess that if it is for a bigger production it may take you more time to use Photoshop and AfterEffects. I use Photoshop for my little film to get they right style for it, but it is a very short film.
Some links:
www.awn.com Animation World Net
www.toonboom.com