be blonde: SuD (be yellow) works fine

I would accept a phrase like jIb SuD, but not Human SuD. In English a person can be blond, but Klingon SuD isn't specifically for describing hair color, so Human SuD would be like saying yellow human in English.

By the way, SuD means be blue, green, yellow, not just be yellow. By describing hair as SuD, you're also describing people who dye their hair those colors (or maybe aliens with green or blue hair). This is fine, but if you ever want to make a distinction between the yellow sort of SuD and the blue or green sorts of SuD, you'll want to say SuD 'ej wov SuD and light, yellow. SuD jIb 'ej wov the hair is yellow; SuDbogh jIb 'ej wovbogh / SuDbogh 'ej wovbogh jIb hair which is yellow.

be straight (of hair): beQ (be flat)

We have the word wan which means be straight. I don't see why this can't be applied to hair.

be curly: gho rur (resemble a circle)

If someone said gho rur jIbDaj his hair resembles a circle, I wouldn't understand. I don't have a good alternative, though.

be wavy: yu'eghmey rur (resemble waves)
be bald: jIb ghajbe' (to not have hair)
be hazel: SuD 'ej wovbe' (be yellow/green and non-bright -- I thought "SuD 'ej Doq 'ej wovbe'" was too unwieldy)

I would consider SuD 'ej wovbe' to be blue. Hazel, the color, is light golden brown. Brown is Doq 'ej wovbe' (so how to say light brown is unclear to me... maybe Doq 'ej loQ wovbe'?). The color gold is a sort of yellow-orange, which would be somewhere between Doq and SuD 'ej wov. Hazel eyes shift between brown and light gold, sometimes with blue in them. There's no way you're going to get Klingon colors to describe them simply. Even in English, hazel is just a way of saying, "it depends."

freckles: DIrvemmey (skin-mark-PL)

You should put spaces between nouns.

vem seems to me to be tracks or marks left behind by something making them, not naturally occurring features. I don't have an alternative.

wrinkle: bentlhegh (age-line)

This is an interesting construction, but I don't know if ben can refer to age like that.

glasses: mIn'al'onmey (eye-glass-PL)

I would figure that out, but I highly doubt that would be the real term. Maybe mIn laH tI'wI' or something similar.

braces: Ho'baS (tooth-metal -- it's singular -- as I understand, they say the singular "brace" in British English, so this has precedent)

I would understand this, but as with glasses I don't know if this would be the way to say it. I would imagine Ho' wanmoHwI' or Ho' wanmoHmeH baS or something like that.

In Klingon, in most cases, all nouns are inherently both singular and plural. That is, if I say the word Ho' it means both tooth and teeth. Context or grammar may make it explicit, but you can't just take the word Ho' and force people to interpret it as singular.

tattoo: DIrmIllogh (skin-picture)
jeans: yopwaH ghegh (rough pants) -- and I also notice "yopwaH buq" for "pants pouch; trouser pocket" -- how about buq yopwaH for cargo pants?

I have no problem with these as descriptions of these things, though I wouldn't expect them to be THE terms for them.

polo shirt: wep yor poSmoH ([sleeved] shirt with open top)

This says jacket it causes the top to open. Notice that wep is a regional-only term for sleeved shirt; outside of whichever region on Kronos it means that people will assume you're talking about a jacket. There is no standard term for shirt, but there is a description of a t-shirt, which is yIvbeH SeQHa' informal tunic. Now, a polo shirt isn't as informal as a t-shirt, but it's not exactly a tunic either. Its defining characteristics are that it is short-sleeved, heavier than a t-shirt, and has a collar. Given all that, I might compromise with mongDech ghajbogh yIvbeH SeQHa'. Not perfect, but that's what you get trying to translate between cultures.

tank top: be'nalmoqwI' (a calque of the English wifebeater)

NONONONONO! Ugh! The term is bad enough in English without porting it to Klingon.

Just say tlhay ghajbe'bogh yIvbeH tunic without sleeves.

headphones: nachQoywI' (head-hearer . . . a calque from the German Kopfhörer)

Another one I would figure out which I wouldn't use. I'd say qoghDaq QoymeH jan tuQbogh hearing device which one wears on/in the ears.

skateboard: rutlh'echlet (wheel-board)

I'd get it.

guitar: javHurDagh (six + stringed instrument)

I wouldn't get it. If you don't want to approximate by just saying HurDagh, be explicit and say jav SIrgh ghajbogh HurDagh. Or use a foreign term and say guitar.

bass: javHurDagh jaQ (deep guitar)

I don't think jaQ means that kind of deep.

be teenage, be adolescent: nenchoH (become adult)

Your translation of nenchoH as become adult is correct, but become adult doesn't mean be teenage; be adolescent. nenbe' not mature; nenHa' immature; wej nen not yet mature. I don't have any simple translation for teenage that isn't literally just more than twelve, less than twenty.

teen, adolescent, youth, young adult: nuv nenchoH (person becoming adult)

nuv nenchoH is a nonsensical phrase saying he/she/it becomes mature, person. If you want to say the person is becoming an adult, say nenchoH nuv. If you want the person who is becoming an adult, say nenchoHbogh nuv.

-- 
SuStel
http://trimboli.name