Color Choices

When I cruise through patterns and projects on Ravelry, I am often amazed by the colors people have chosen for their projects.  I wish I knew the secret codes of how they come up with their color combinations.

For example, one of my favorite projects EVER, is this pair of mittens by Ravelry user helloyarn (I'm pretty sure I've posted about these before, back on the Fiber Freaks blog).  Seriously.  I would never have thought to use a bright turquoise and a purple together, but it looks AMAZING.

There are several Truckee Shawlettes I adore, but one of my favorites is this one by Ravelry user Honeybee52; the contrasting colors are excellent!

And then, there's the Color Affection projects, of which I have many favorites (like this one, this one, and this one).

I understand that a lot of this (magical) ability is an understanding of color theory.  So many of my crafty passions require the use/knowledge/understanding of color theory (cake decorating, knitting, make-up), that you would think I would get it, but apparently not.  I am still constantly befuddled.

Awesome color theory poster by Nathan Bilbao.

I've read articles and watched YouTube videos all about color theory, but its still not clicking.  If anyone has any tips, I would love the help!  I'd like to (re-)try fair isle knitting again someday, and having a better grasp of color choices would definitely help.  Plus, now that I'm interested in dyeing, color mixing really does need to creep into my brain, or I might end up with some not-so-pretty results.