A flop with one, two, or three suits.
On a monotone board someone may have a flush, so a Strong one pair drops to Medium. A rainbow board has no flush draw; if the ranks are not connected, it is also dry. Example. K♠ 7♠ 2♠ is monotone, K♠ 7♠ 2♦ is two-tone, and K♠ 7♦ 2♣ is rainbow.