Here's tonight's progress scan!!
OK...tonight I decided to take some VERY big gambles that I hope are going to pay off as I finish this thing even though right now they look kinda rough.
First, I decided to really bring out the shadows that are in the source picture and allow some real contrasts to appear. It looks like a lot, but I am hoping that once he's completely finished and the lighting over the entire piece becomes evident, that these shadows will make sense.
Second, I decided to try and pick up some of the hues of the lighting. This is something I've never had to deal with before on a portrait since I've only thus far done them in black and white--but I thought letting some of the surrounding light play off of his grey skin might give further warmth to a character who may look like a big, tough guy on the outside but is really all about love.
PLEASE, if you see me about to destroy this, let me know--now is the time!!
Meet Legate Tekeny Ghemor, a Cardassian dissident from
Star Trek: Deep Space Nine, a very honorable character with a special attunement to matters of the heart even while caught in a political system that seems to do its best to suppress every sign of compassion: a father who will do just about anything for his daughter's good--even if that means giving her up. And even when he found out the truth (see the episodes "Second Skin" and "Ties of Blood and Water"--I'm not gonna give spoilers!), he didn't let matters of race and politics stand in the way of real fatherly affection.
Here is the reference I'm using: http://www.memory-alpha.org/en/wiki/Image:Tekeny-Ghemor.jpg
Not as big as I would've liked, but between that and watching "Second Skin" again, I think I can do a passable job.
While I'm rather far along to make certain changes (i.e. the placement on the paper--but damn it, I am NOT throwing this out at this stage...too much good in it!), I wanted to show you this WIP. I intend to scan this drawing every night as I complete the day's work on it, to preserve it in case anything should happen. This is the first time I've EVER attempted a color portrait, and I felt that experimenting on a character with whom I need not be that realistic (in terms of matching skin tone and the like) would be a good way to start.
Plus, when I saw the grey paper I had on hand, it was just
screaming for me to draw a Cardassian!
A special shout-out goes to

here on SheezyArt, and
Robert Sloan for their wonderful work with colored pencils and colored paper, which was the inspiration behind my taking on something this ambitious. Thank you very much to both of you guys!!!
Comments
Don't be afraid of working with shadows; that's where the piece's depth will come from. You always need to push it just a little further than you think you should. Build it up in slow layers, and then as a very last step, lay down some very heavy, small touches of super-dark shadow and super-light highlights. These will make everything pop. But it needs to be the last step, because once that's down, you can't go back (without working at it with a knife, and then you run all kinds of other dangers.)

Adding some hue is a great idea. I'd handle it by using complementary colors...one for the highlighted areas and one for the shadowed areas. Like a warm red-brown against a cool blue-green. The eye sees through contrast, ya know?
This is looking really fantastic so far, though. Be brave!
Lindale Says:
What JoJo said
The reference picture's useful from an information point of view, but bringing out the shadows is a good idea - it'll make it more eye-catching.
It means that you can try out a bunch of ideas and then by the time you're working on the picture you already know whether something's going to work or not.
But this is really looking great so far :)
And I've probably waxed lyrical about this before, but having a second piece of the same paper just for experiements can be beyond helpful
I usually went about conventional drawing in a bit of a different way, and drawing things this way usually doesn't work for me, so I'm reluctant to say much else.