Combine Network Into One Site?

[Trivum]

I have a network of somewhat related niches. I'm thinking of combining them into one larger site.

For example, my sites are Blue, Red, Green, Yellow, etc.

I'm thinking of combining them into one site called "Colors" with different sections: Blue, Red, Green, Yellow, etc.

Do you think this would hurt or help in terms of SEO?

I realize the larger site wouldn't be as niched, but I'm wondering if bringing all the different PR power together might help the overall network. In other words, would bringing a PR4 site together with four PR2 sites and three PR1 sites, etc. help the less powerful sites? Or do you think it would just dilute everything?