Choosing the right color denim to match a brightly colored shirt comes down to a matter of proper contrast and color balance. After all, the idea is to flatter your best features, so your denim color choice is dependent on the color of the shirt. For instance, there is a difference in the denim color you might choose to match a bright yellow shirt than what you might choose to complement a bright blue hue.
Bright Yellow Top, Dark Blue Denim Jeans
Dark denim jeans add an air of sophistication to an outfit and make the color of the shirt pop even more, particularly when the contrast is as dramatic as a pair of dark blue denim jeans and a bright yellow shirt. This color of the denim to match a yellow shirt should be a midnight blue hue to complement the yellow; any other color may cause the entire ensemble to look washed out.
Bright Red Top, Black Jeans
Red and black is a fail safe color combo and this is demonstrated perfectly when you pair a bright red shirt with a pair of black jeans. The trick to pulling off this particular look is be sure that your jeans have not faded to gray but are a rich black hue. Black jeans look good with just about any shade of red, so you have a number of different shirt options here.
Bright Blue Top, Light Blue Jeans
This color combination only works if you have a fairly lithe body type. Otherwise, the bright blue top will call attention to your bust and midsection in a fairly unflattering way. The contrast of the blues works nicely here and the light blue jeans serve as a backdrop to the brighter shirt. You can have fun with accessories with this outfit, with silver making a particularly nice fit.