Last year Royal Mail made a significant change to the red color used for first-class Machin stamps. It was made darker and less yellow to better match their official brand color used on vehicles, post boxes, publications, etc.
The complete set of changes in this rebranding effort were discussed in this blog and in the Norvic Philatelics Blog.
Now catalog editors have the fun chore of deciding whether to recognize this as an official change and what to call the new color.
Royal Mail's name for the original color, introduced in January 2013, is Royal Mail red. This is what appears in the margin of the sheet stamps. We haven't yet seen sheet stamps in this new shade and Royal Mail hasn't indicated whether they will change the name of the color or not.
The 2013 version is on the left above and the new stamp on the right.
The Modern British Philatelic Circle used Royal Mail's name for the original color and is calling the new color Royal Mail red+. Douglas Myall, in The Complete Deegam Machin Handbook, also used Royal Mail red for the original and is calling the new color Royal Mail red 2, abbreviated RMR2.
Stanley Gibbons called the original vermillion and is calling the new color bright scarlet.
Here in the US, the Scott Catalogue editors are, as of this writing, still thinking about whether to recognize this new shade at all, and if so, what to call it. The 2013 issue is called bright red. I'll update this post when I know what they've decided.
As long as it's open season, what's your suggestion for the name of this color?