There's got to be a real expert around here somewhere, unless you have a Tandy leather outlet nearby with a knowledgable owner.
BUT...when I was coloring some chap suede straps for a set of armor, I was told by a dealer that the nap of suede makes re-coloring it by any method difficult. I don't think it's impossible, but it may not turn out the way you want it because the nap will soak up moisture. Plus, if the boots have been treated with any kind of repellent or finish, you might be SOL regardless.
I did manage to tint suede using watered-down acrylic paint, but the dealer was right, it was very difficult. Plus, lighter colors caked no matter how much water I used and how many layers I applied, while darker colors just soaked right in. So I don't recommend it. If you can't find an expert in leather dye to ask, try buying a small, untreated piece of suede leather (many craft stores have Tandy products, including leather scraps, or there's also the suede patches for coat elbows) and test out the dye first.