About two years ago, the house brand at Lowe's got the best rating from Consumer Reports. It's called American Tradition.
I really like Miller Paint Co in Ballard, they were helpful and non-intimidating when I was a novice DIY painter.
Best Paint has low- and zero-VOC paints if off-gasing is a concern.
Professional painters really like Benjamin Moore paints, which you can get at Seattle Paint Supply.
Lowe's and Miller Paint are open on weekends, I don't know about Seattle Paint Supply or Best Paint hours.
No matter where you go, they should be able to match any paint chip or swatch of color you have in hand, so if you find a chip you like, you aren't limited to a particular brand.