This outfit features a 'triadic' color scheme: colors that are evenly spaced around the color wheel. This is a great approach for a colorblock look, since the colors have such striking contrast to one another. With this one I used the navy blue to evenly divide the different sections of the outfit, and made sure all the other pieces were large and continuous chunks of solid color.
Generally when I mix colors in an outfit I like to use different shades of the same basic hue; however with a colorblock look it's really better to match the colors where they repeat or else the effect is lost. Thus my hat, belt, and shoes are all exactly the same shade. Compare today's outfit with this one, where I mixed up several different shades of blue and green for a completely different look.
Cardigan: Max Studio
Obi belt: Sunhee Moon