There are, but the "Mil Spec" color is it's own ( attractive ) color, don't think it's trying to be an FDE, if you want to match it, you'll have to break out the cerakote...
Yeah there are a heap of shades. A FDE FN SCAR has at least three, one for the upper, one for the lower, one for the mag, or something like. But that's not always so bad. The way HK does with their greenish lowers and lighter, more tan uppers looks pretty good on their G28 DMR, for example.
And cerakote, duracoat, krylon, whatever will fix it right up if you don't like it!