What kind of pants should you wear with a really colorful top?
The first thing I need to know is if that print is appropriate for your shape and stature. Be careful not to overdo a print...or underdo (for that matter!). The print you wear should be in direct proportion to your stature. In other words, if you are petite, then steer clear of wild, bring, large prints. Likewise, if you are a statuesque lady, steer clear of small prints like a calico.
To answer your question - assuming the print is in proportion to your stature, and that your body shape can handle the bright print...then go with a solid in a neutral color. Pick out one of the tones from the shirt, and wear that. Look for colors like brown, black, white. Something that won't compete with the 'wow' of that print.