Almost everything that I have learned is from reading blogs and following colorists on YouTube. There are many talented artists who put up different types of videos and there is a lot to be learned out there. A few of my favorite artists are:
She frequently reviews various coloring books as well. She also has some speed coloring videos – where there is no explanation, just her coloring a page. You can also visit her blog at La Artistino - Peta Hewitt
These are just a few of my favorite artists. A quick search will get you hundreds of channels to follow. Watch some videos for inspiration and get coloring!