accurate shades

MM has a large number of FS matched colors as well and ANA (US WWII) RLM (German WWII) and other specific colors. They are not adjusted to scale effect and any paint in the field will vary according to batch and fading.
The MM match is to FS395a color chips and codes. FS numbers look like this: FS 34097 (aka dark green -as used on SEA camo in the 1960's)
The first digit refers to reflectance (1=glossy, 2 =semigloss, 3 =flat). The second digit is the general color (4=green) and the last three digits are the shade with low numbers being darkest.

They have a large number of paints matched to that standard, but they don't have all the paint colors that cover the standard. Far from it!

I use Gunze and Lifecolour paints, and in each case these are referenced against an FS number, so even where they are labelled as a colour specific to one use, they can be used for another.

An example being Gunze H312, which is labelled as IAF Kfir green, and is FS34227 which is in fact the same as RLM99.

Karl