craftgrrl | Anyone here up on dyeing?

I was hoping that someone here would be knowledgeable about dyeing fabrics:

I have an army bag that goes over my shoulder, its big enough for a lunchbox perhaps - not like a messenger bag. Its made from very thick canvas - its super hard wearing and great.

The only problem is, I bought it from an Army Surplus when I was 14 and not all that stylish. So I bought one that's dyed purple. On its own, fine, but the colours I like to wear are red and denim and lots of colours that definitely do not go with purple. So what I need to know is - how can I dye this bag black? The canvas is so thick it won't soak up water (with dye in) like normal material would. Could I paint it on? Would a washing machine dye be absorbed?

I'm really keen to have a fancy black bag, so if anyone could help I'd be grateful as anything.