I must admit that I imagined Adm. Richards as a "nice old man" - a kind of "innocent", much less sour looking appearance which hides his true nature as an intel. admiral.
Forstschen and Keith are pretty sparse with descriptions of him; he's usually described as a bald, lanky, tired-looking old man, if that. (Forstchen from my reading of him is pretty sparse with descriptions in general, but that comes off even more when Richards is concerned.) I think there's a passage in False Colors during his introduction where Bear, about to meet him for the first time, thinks about how shifty the popular image of him is, which contrasts to his somewhat unimposing actual presense.
That said, this portrait and mannerisms fit extraordinarily well with the overall background and 'feel' that Arena in this incarnation was going for - a very kinetic, active, comic-book sense of tension that comes out in a lot of these sketches; but I don't think that any of them really capture that feeling as well as this piece right here, with the spook-turned-swashbuckling-space-hero (fighting-admiral?) transformation. I'd like to have been able to see Kruger in this style; the man's craggy demeanor seems to fit this artist perfectly.
As for appearance; well, apart from complexion the one thing that came to mind was the rather large and imposing nose (something which I'd think would be hard for others to miss unless Richards, good spy that he is, is trying out a new look). His face in general brings to mind gruff Admiral Wilford, as well as a number of other actors and/or historical personages that slip my mind.
(Actually, his overall bearing reminds me somewhat of James Mason.)