It's a bit awkward to end up wearing the same color as someone else.
Tips
usage
Two senses: (1) fashion-positive — deliberate bold color blocking; (2) fashion-negative — two people accidentally wearing clashing colors. Tone of voice decides which.
memory
撞 = to crash / collide, 色 = color. Colors 'crashing' into each other is a vivid image for both senses.