The phrase "be striking" carries the connotation of something that is noticeable, distinguished or impressive. Its antonyms, on the other hand, suggest the opposite: ordinary, unremarkable, and unimpressive. Words like "inconspicuous," "delicate," and "subdued" describe things that blend in or are easily forgotten. "Unremarkable," "unmemorable," and "undistinguished" suggest a lack of uniqueness or distinctiveness. The antonyms of "be striking" can be used to describe things that are plain, average, or simply forgettable. In summary, the antonyms for "be striking" express the inability to catch attention, and they are the complete opposite of being remarkable or memorable.