in AM, use 美国英语用 discolor
										- V-ERG (使)变色;(使)褪色
 If something discolours or if it is discoloured by something else, its original colour changes, so that it looks unattractive.- A tooth which has been hit hard may discolour...
 受过重击的牙齿可能会变色。
- Some oil had seeped out, discolouring the grass.
 有些油渗出来了,把草地染得变了颜色。