I'll join those saying you need to be prepared for it all to go wrong.
The stud fee is actually one of the smallest expenses for putting a foal on the ground - if you plan to do it all "properly".
Where are you located that color is expensive? I've found paints all over North America - most going for less than $1000 these days (foals). You could buy a foal you like, from photos and video, and ship it in too - would probably still be less of a gamble than breeding. (Normally I wouldn't recommend anyone do this... but... it's certainly not a whole lot more of a "risk" than it is to breed your own foal - especially if you want color)
Yes, you can "guarentee" color - as in if you were to breed to a homozygous Tobiano - you'd always get some form of Tobiano. (an example) That said, there are a lot of different levels of expression for that gene. I have a Tobiano that ONLY has high white stockings (she's been DNA tested, so DEFINITELY Tobiano)... so even if you "get" color, you may not "see" it.
I too have a "Pintaloosa" who didn't get any spots to speak of. I was big time bummed at the time he was foaled - but he's more than made up for it with his personality. He popped out chestnut with a big blaze and 3 high stockings... and one loonie sized white spot on his belly. He's still super cute, but not at all what I was "hoping" for. LOL He's a really well built horse and tends to prove it by winning open halter classes.... so it wasn't a total loss - but I'm REALLY glad I chose parents who were well built to start with and the color was to be "icing on the cake".
What I WOULD make sure of, if you did decide to breed your mare, is that you have someone help you pick out her weak points, and then help you find a stallion who is strong in those points. By doing this you'll reduce the chances of ending up with a non-colored foal who ALSO has poor conformation.