Older stamps seem to be the best for finding monochromatic colours and these ones were issued between 1957-1961
Three stamps from Selangor, a state of the Federation of Malaya, each with a portrait of Sultan Hisamuddin Alam Shah (full name Sultan Hisamuddin Alam Shah ibni Al-Marhum Sultan Alauddin Sulaiman Shah)
He was the Sultan between 1938–1942 (with a break during the Japanese Occupation) and again from 1945-1960.
and this one showing a tiger
I have three of these and each one has a slightly different shade of 'violet'
It seems the tiger was a popular image and was used for the other states as well though each with a different image in the medallion. In the bottom plates of each the left shows the coat of arms and the right the value.
The stamp for Penang has in the medallion the coat of arms while the one for Trennganu (now known as Terengganu) has Sultan Ismail Nasiruddin (full name Almarhum Sultan Sir Ismail Nasiruddin Shah ibni Almarhum Sultan Zainal Abidin III). His reign as Sultan lasted from 1945-1979.