I see. Well, using photoshop is a good idea. And if you don't have that, use paintshop. Most computers should have that program on them by default.
I myself don't think I'm ready to get into cg just yet. I could make a cg picture, but I wouldn't be too confident about it like I am with my non-colored pics. On some levels though, using photoshop is almost like cheating, as its point and click and doesn't literally require a natural talent. I prefer to use what I've been given, and rough it with natural tools, then to take what can be considered the easy way out. For me, at least for now, it feels more real for the picture to be colored using some type of pencil rather then a computer program.
For example, my latest picture (for this theme, not a regular picture) is going to be colored and the coloring medium of choice for me are colored pencils. Some people may think its tacky, but in the hands of a skilled artist, they are just as good as any computer program. Although, its been years since I've even colored anything or used colored pencils. So I suspect my coloring ability for the picture will be average rather then great.
So anyways, I'd suggest you just keep using colored pencils. The reason you shouldn't use markers is because they leave streak marks on the picture if your not careful, and that can ruin the look of a picture.
- Damien