FS conversions to MM and Tamiya

True, but the FS, ANA, BSC, RAL, or RLM colors are usually specified by the build nation and service as to how an actual piece of military equipment is supposed to be painted. Often with a standard specified pattern as well. While model paint directions may not be the last word on that subject, one can usually find the correct information on the Internet without too much trouble nowadays.

I have found that the FS numbers bear very little resemblance to the colors you might see on the painting guides included in some of the better kits, which include full-color prints of the model.  Following the FS guide numbers gives me a model that looks nowhere like the painting guide sheet.

So I don't worry too much about it, I just improvise until I like the results.  I think the colored guide sheets are painted by artist who has no idea of FS colors.  So just wing it, until you're happy with the results!

I use:

http://www.paint4models.com/

It all comes down to a science determining what's good enough for you by brand.

http://www.ipmsstockholm.org/colorcharts/stuff_eng_colorcharts_fs.htm

Get free imodelkit for the iOS. You can xreference pretty much any modeling paint.