Ardi's sketchbook

[Ardian Gashi]

Here some foreshortening practice I did, half of the page is from a Loomis book, the other half, I just went to quickposes, and tried to breake down some stuff and filled a couple of other pages.

A quick question for the apple studies, I played a little bit around with adding color to a grayscale. I never did that before, I always just went stright in with color, just chose a base colour and so on. I watched Dave Rapoza's Bog Witch tutuorial while painting and tried to use the same process (more or less). I painted the grayscale with a multiply layer, then soften some edges in a normal layer and added the colors with a soft light layer. In the end it came out rather muddy and washed-out. Well the grayscale wasn't that good to beginn with, in retrospect I didn't invest too much time on it, which I should have done so and Dave did some things in his tutorial that I probably just missed, even if I didn't missed them, it's still my first attempt, so I was in one way or another prepared to fail, but I digress. 
And finally my question, how do you all add color to a grayscale? Just curious. I'm going to look up some ways on my own, and it's mostly just practice at the end of the day. Of course it looks good when Dave does it, since he has years and years of experiance, so my expectations weren't that high. But since I'm in this forum, there is no harm in asking such things.

Thanks in advance, if someone chooses to answer.