They both look awesome and so does Castiel. I am with Alex in that I love Castiel's rocking design. =D
I don't think this was put in here before so here's Sienna's picture of Hannah trying to imitate Lokka's coat. XD
Kinda looks like you just used the fill bucket on lineart that's merged with a white background, best way to colour in photoshop is to create a new layer underneath the lineart thats just the black lines on their own layer, then use the selection tool and outline the area you wish to colour (following the lineart of course) then using the fill bucked on the area of the new layer. There's probably other ways but that's how I do it.
gimme a hug because we are internet bros by incidence
What I generally do for scans is I create a new layer, and for layer type (for coloring) I use the layer type Multiply. that way wherever you color, your lines (if they're darker ) will always show up on top.
If you don't have a tablet (like me and do all your stuff by mouse) one of the ways to color between the lines is to use a Polygonal Lasso (or for that matter any lasso, but for a mouse Polygonal may be easiest), making a selection of a specific area. It's slow, but then so is coloring with a mouse anyway.
Also, if your lines don't show up on top of your stuff as much as you'd like them to, try increasing the brightness/contrast (more contrast) of the scan.