A black shirt worn with khaki pants is perfectly acceptable. Many style experts now even encourage combinations of khaki, black and brown. Contemporary standards have more to do with balance and personal style than the old prohibitions on color mixing.
The advisability and appropriateness of color combinations has as much to do with the kinds of garments involved as the colors. A black polo shirt with khaki slacks may overwhelmingly suggest a trip to the golf course, but a stylish button-down shirt in cotton or linen creates a more sophisticated impression. Khaki and black are both technically neutrals. Making one the primary and the other an accent color is attractive, suggests Global Post. Adding a third accent color that balances the two makes for an even more stylish look.