Are your 'technical writings' in Standard English?

Why don't you want to repeat a word in a technical document, where the prime objectives are clarity and ambiguity? One way around it is to make a list, such as "Shirts must be: ..."

@BillJ That is my intent, of course. And of course, it is obvious that English is not my native language. We don't even use Latin alphabet here.

@WeatherVane Yes, I understand your point. Probably you are right and I don't need to worry about.

I think only your 4th bullet point is a good use of one because shirt is already in that sentence (not a previous one). Alternatively rephrase the whole section. "Advised colour of shirts: Red to cause offence, white to..."

If you want to look fresh - it's red (informal) / When you are in doubt - it's green. etc. (It does not matter that the referent of "it" can be "the shirt", "the colour" or "the choice.") You have given a general example, but although "is" works with the verb to wear and shirts, it may not work with other contexts and verbs. (Students rarely understand how important context is in English...)

You could, with this example, delete as far as << If you want to look offensive, wear a red shirt. If you want to look fresh, wear a white one. When you are in doubt, green. If you are worry that the shirt might become dirty very quickly, black. >> This is becoming less formal, though. I don't think your example is in the right register to demand an answer that would be appropriate in technical writing.

English readers don't generally register the repetition of pronouns, the way we register the repetition of nouns, so just use one many times.

Sometimes such repetition is good, as it helps to hammer home your point.

What sort of technical writing? Generally as a reader, I'd prefer a table than bullet points like this, however you phrase it.

A general tip: When writing technical texts, just scratch the no-repetitions rule out of your head. Clarity is paramount. You could even use "shirt" four times here.

Wow, it's strange to see the comments were moved here. There are plenty of questions on the Stack Exchange sites that have dozens of comments. Someone had a bad mood?

I want to say "thank you" to all you guys. The suggestions above are really handy.