I don't get it. What does this tool accomplish that isn't accomplished by putting the collected color definitions in a second style sheet and "cascading" it with the standard bootstrap.css? (I'm really asking not being sarcastic.)
A lot of people can't/don't use LESS, which means that a lot of precompiled rules have to be overriden in a tiresome way. For instance if you change the grid sizes you have to adjust a couple different CSS attributes. This tool generates everything in a precomputed easy to digest manner.