On 23 August 1997, Pos Malaysia released a set of stamps to commemorate International Year of the Reef. Four stamps with denominations 20sen, 30sen, 50sen and RM1 depicting marine life of coral reef were issued. For normal lithographic printing of Malaysia stamps, four colours are used i.e. red, blue, yellow and black. I spotted a 20sen-stamp with yellow colour omitted (see below: right stamp). The omission of yellow colour only affects the image of Tubastrea.
The right stamp is a normal copy; the left stamp is flaw copy with yellow colour omitted.