Malaysia (Perak) SC 151 Color Difference

I have two copies of the 15c Malaysia (Perak) butterfly type (Sc 151). Is the color difference I am seeing a real variation, but not listed in Scott, or is is a changeling? And if it is a real variation, what is a more comprehensive catalog for Malaya/Malaysia than Scott?

Thanks for the help.

Check under your loupe.
This stamp exists as Litho by wilkinson (1971) and photo by harrison. (1977) (Chalky Paper)
Minimal value both used.

Mint harrison $15 malay 1997

I have seen variation even with same printing type for these issues. Stanley Gibbons provides more details than Scott to help identify.

Thanks for the knowledge.

Reviving an old topic.

I have encountered the same issue on these Malaysian stamps, again on the 15c issues for both Selangor and Trengganu. In my case they are both the Litho issues and not the Photo issues. The colour variation is significant varying from yellow to lime green. All the examples that I can find online are the yellow ones. Neither Scott nor the SG catalogues that I have mention anything about these colour variations. Has this been updated in more recent SG catalogues as an actual variation?