That "trick" of using a colon before camouflage is misleading. Generally speaking, in written forms, that refers to something previously mentioned. For example...
"The zebra has stripes for camouflage. That's what that is called."
In my example, the first that simply functions as a "pronoun", standing in for the word camouflage.
The word what also effectively functions as a pronoun (it just refers back to the first that).
The second that isn't quite so simple, in that you can't say it represents one or more preceding words. Loosely speaking, it stands in for the fact that (or, reason why) the zebra has stripes.
The actual punctuation in OP's sentence is a matter of style. Valid alternatives include a comma, period, or dash (they all just represent a "break/pause" in speech). The important thing is that either [whatever is being identified as camouflage] should already have been mentioned in the discourse, or the speaker should be pointing at it as he speaks
It's sometimes okay to use that as a "forward reference" for something you haven't yet identified by anything you said or wrote earlier, but this would normally require a very strong implication that the speaker (and probably his audience, too) are at least thinking about whatever that refers to, even if they haven't specifically mentioned it.
Assuming that OP is concerned about whether he can validly use that twice in the same utterance, the answer is "Yes". In this specific example, they refer to two closely-related referents (a word, and the thing represented by that word). But the referents can be completely different...
"Where's the zebra? It's hidden in the grass. That's where that is"
(first that = hidden in the grass, second that = the zebra).
...or they can both refer to exactly the same thing...
"What's hiding in the grass? It's a zebra. That's what that is"
(both that's = the zebra).
Best Answer
I think a native speaker would understand, but it is gramatically correct to say "which there weren't".
I think this is because you can count eggs and say that eggs "were" or "weren't". Substitute in a mass noun like milk, then you should say that milk "was" or "wasn't".