用一支2b画副灰色背影
[yòng yī zhī 2b huà fù huī sè bèi yĭng]
Using a 2B pencil to 'draw a gray back shadow'. Here, 2B pencil implies simple tools and materials for drawing, while a grey shadow suggests something bleak and sorrowful - perhaps a sad memory left behind or the silhouette of lost love.