I disagree that light, steel strings equal bright tone. I play DR Hi-Beams in ridiculously light gauges (my E is .95) and can get a really dark, thick tone. The key (for me, at least) is super low action and keeping my attack very light. You can look to some of Gary Willis's writing on that point.
The previous posts mentioning how much control over your sound is in your fingers are dead on.
The previous posts mentioning how much control over your sound is in your fingers are dead on.