draw/paint software
For me it comes down to what software I have at my disposal and how likely I am to learn it and create with it. If you really have a desire to draw, paint and create, you'll find a way with whatever software you can get.
When you are able to get your hands on new software, try it and see how it feels. I use Photoshop because it's what I've had longest and feel most comfortable with. I started years back with Ulead's Photo Plus (I think that was the name) and then got Photoshop sometime later. I also use Procreate Painter Classic sometimes, which came with my drawing tablet.
As far as coloring goes, nearly any paint program will do the trick so long as it supports layers. You really want that ability so you can work without damaging or covering up the original pen/pencil work. Then just practice to find methods of shading and highlighting that fit your style. Some swear by Photoshop's Burn and Dodge tools, and others prefer to use paint brush strokes with specific colors, and there are probably dozens of other ways to go about it.
However, the point is, you don't need expensive software. The desire to create artwork you like will supercede any shortcomings in your tools if you put forth some time and effort to get creative with the software. The end results, and your happiness with it, are far more important than the tools that got you there.
Oh, and another idea...if you also desire a drawing tablet, look for them on Ebay, or the low to mid-range models, and you'll find that many come bundled with good selections of drawing/painting software.
-Korrigan
MET2