Perhaps these previous topics will answer your question

• Is there a consensus on why "blue" does not appear in ancient texts?

• I recently read an article that stated most cultures didn't identify the color blue until modern times. Can anyone verify how accurate that is?

• What color was the wine the Greeks were drinking, if they associated it with the sea?

• Did the ancient Greeks really have no word for the colour blue?

• Did medieval people perceive colors the same way as we do?

• What did Greek people look like 4000 years ago?

I can't directly the question as it relates to Egyptian pre-2500 BCE texts, but you might find some food for thought in this older thread on later languages that didn't have a detailed set of terms for shades of "blue".

An Egyptologist would be able to give more details, but I can at least point out that Egyptian texts earlier than 2500 BCE are very few and far between. Even connected sentences in writing were a relatively recent invention at that date. So making inferences about colour terms based on evidence that fragmentary would be sloppy methodology to say the least.

Ultimately it comes down to how different languages divide up the colour spectrum. It's got nothing at all to do with sensory capabilities, and nearly nothing to do with perception. If your world doesn't have a huge amount of a given colour in it, there's not much point having distinctions for every minute shade in the colour spectrum. I say nearly nothing because colour terms can have a measurable, though small, impact on cognitive organisation of colour perceptions, and speakers of a language without finely grained colour terms can take longer to organise sensory perceptions of colours that their language doesn't distinguish. I emphasise that that's a matter of cognitive organisation, and not a difference in sensory capability. The /r/AskAnthropology crowd would be the best equipped to give details about that.