Hurgh and SuD are both verbs, so you can't put them in the same sentence without some sort of marker to connect them. SuD 'ej Hurgh generally refers to the darker end of the "cool" spectrum - what we might call "dark blue". There is a theory that klingons cannot see purple, or at least cannot perceive it as a single color and the only way we have to describe it is Doq 'ej SuD.
If that's true, that means that Klingons are color blind - they must either have deuteranopia or deuteranomaly!
Not so much colour blind as just having developed vision in a different spectral range. In one of the novels, I think it's Pawns and Symbols, a DIvI' crew discovers that Klingons can't see red. A Klingon enters a restricted area and doesn't understand how he was supposed to know that a plain black door designated restricted. The signage was black on red. In the novel, the Klingon can see two colours into the ultraviolet, colours he calls kalish and amarklor. Either way, it's a difference not a deficiency. Neither the gymnast who can't deadlift double her weight, nor the powerlifter who can't do a back walkover on a balance beam is physically inept.
That novel has been contradicted by more recent canon, by the way. Klingon for the Galactic Traveler says, "The fact that neither SuD nor Doq includes what is called ‘violet’ or ‘purple’ in Federation Standard may be related to Klingon physiology—that is, exactly how the Klingon eye processes different wavelengths of light," suggesting that Klingon vision might be skewed the other way (especially since Klingons DO have words for both 'red' and 'black').
Technically, SuD 'ej Hurgh could also mean 'dark green', I would think. When the basic color terms are this vague, the terms for dark blue and dark green are not necessarily mutually exclusive.
Yes, it is an accepted translation. That comment may have seemed a bit redundant and/or out of left field, but if one is going strictly off the "best," or default, course sentence translations alone (and not reading the comments), one could easily get the idea that SuD predominantly means "blue," when really, that isn't correct: it means all cool colors - blue, green, yellow, and everything in between - equally. That's the point I was trying to make.
It would be interesting, at this point in the course, to come across a sentence like "the book isn't blue, it's green." :-) In order to get that idea across, I understand we'd have to use similes, saying something like (let's see if I can get the grammar and word order correct) SuDbe' paq chal rur; SuD 'oH tI rur, but chal and tI aren't words we've learned yet, so it wouldn't really be possible to introduce such a sentence without it being very confusing. But, I think you see my point. The colors can be a difficult concept to grasp.
Russian has two basic colour names that divide the colour space we call blue. If you call something синий but it's actually голубой, you're as wrong as if you said a blue thing was green, but in English if you call something "blue," no one is going to say "no, it's light blue" because everyone understands that light blue is a subset of blue. SuD 'ej wov is a subset of SuD and if you're a Klingon web designer you can pull out whatever the Klingon retina makes equivalent to RGB, values to further refine the colour. But a Klingon visiting Earth might compliment us on the multitudinous "blues" of our planet: jul SuD, magh SuD, bIQ'a' SuD, Deb SuD, chal SuD je. yuQ SuD ponglu'.