The links provided by /u/Searocksandtrees answer your main question regarding the actual history. If I may, I'd just like to to reply to this bit:

And, since there was no word for it, we may not have even recognized the color.

This is linguistics, not history, but on this subreddit dedicated to serious, academic-level content I did not want to leave that statement unchallenged.

The idea that if a culture doesn't have a word for something then they may not see or perceive that something is called linguistic relativity or more commonly the "Sapir–Whorf hypothesis", after the people who coined it. (The trope that "eskimos" have 100 words for snow (or even more) is also based on this; that trope is completely false) Linguistic relativity was coined a century ago and is still a topic of research, but it's not as popular as it used to be. Early claims have been shown to be overstated. While there sometimes is an effect of the words we use on how we perceive things, the effect is usually small. It's certainly not the case that we don't see things if we don't have a word for it.

Specifically on the subject of 'blue': English and other germanic languages have quite a broad range of what constitutes 'blue'. Other cultures often divide that range in two and use two different words for it - 'light blue' and 'dark blue', for lack of proper words for it in English. Here is someone discussing research into how users of English and Greek perceive different shades of blue and green. Greek has two different words for shades of blue, English does not. They measured brain activity while people were shown series of dots of one shade of blue (or green), with occasionally a dot of a lighter/darker shade being shown. The result was that the speakers of Greek had increased brain activity when the colour switched from light to dark blue (and vice versa) whereas for the speakers of English there was no effect. This shows that words do affect our perception, though the effect was small.

Note that this research shows that English speakers do not have increased brain activity for different shades of blue. This means that they don't spend effort trying to find different words for the shades; it does not mean that they don't see a difference between the shades.

[Note: where I say 'speakers' or 'users' above, please read 'native speakers'.]

Some points...

• Color is a highly cultural concept. In fact, new color words are being invented all the time. E.g. salmon, fuchsia, aqua... are new inventions. The color orange didn't become used until after oranges (the fruit) were introduced in the late Middle Ages.

• The reason why color feels pretty standardized these days is because it is being taught in preschool. It's safe to assume that color words were never this standardized before unless you were a professional painter.

• Color today is often associated not with what an item looks like, but what color you would use to paint it. So it's really a cliché: in kids' paintings, the sky is always blue, the sun is yellow, the grass is green. In reality, the sky is often white or gray, the sun is always white unless it's setting or rising, and the grass is often brown or yellow.

• Unless you are an artist, the practical use of describing things like the sky, the ocean with color words is really limited. I.e., no one cares what color water is except for poets and painters. The only cases where people really care about color is when it is useful to distinguish stuff, e.g. berries or farm animals.

It's simply that different languages divide up the available colour-space differently. As a result, the boundaries of what an English speaker calls "blue" don't line up with the boundaries of what an ancient Greek would call kyaneos.

In modern European languages, words corresponding to "blue" seem to line up with each other pretty well, but even there you don't have to dig very deep to find problems: if you were to take all the English colour terms relating to "blue" -- cyan, azure, indigo, navy, turquoise, aquamarine, and any others that I've forgotten -- and look for parallels in another language you know, it's extremely likely you'd find that there isn't a one-to-one relationship.

For reference, in ancient Greek the word kyaneos indicated mid-to-dark shades of blue, ranging from the colour of a porpoise (Aristotle History of Animals 566b12) to shades that we might call "black" in English (the colour of dark hair, or the feathers of a swallow). That word approaches "black" from the blue direction, in the same way that the colour term melas approaches "black" from a reddish-orangey direction. Lighter and paler shades of blue would be described as glaukos. Generally speaking ancient Greek colour terms have the most distinctions for dark and vivid colours (kyaneos, porphyrios) and for pale, greyish colours (chlōros, glaukos). Pale, vivid colours seem to get dealt with on a more ad hoc basis; an example of the latter would be erythros "red" (mainly the red of a blush, though it could also be used of wine; but not blood, which was melas).

hi! fyi, you'll find some previous discussions on this here

• Why do the ancient Greeks describe the color of the sea as "Purple"?

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

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

ed: found a couple more

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

• What did Greek people look like 4000 years ago?

Others have addressed most of the points here, so I'll just focus on the last one. Krishna and Vishnu are not depicted as blue in ancient Indian texts. Krishna is described as black (black as the moonless night), and Vishnu is described in a dark hue (color of the rain bearing cloud). The only major Hindu god associated with the color blue is Shiva (a blue throat).

The blue you see on images is an idea of representation. Texts and descriptions don't agree with it.