I use Windex-I find it to be a good product-it does a good job for cleaning windows.
My question is: the blue dye in it-does it actually do anything? Laundry bluing actually does-the blue tends to mask the yellowing that white clothing frequently exhibits.
A few years ago, there was a vogue for so-called “clear” products (clear coke, crystal pepsi, etc.)-did Windex ever come out with a “clear” version? Was it popular?
I’d guess its main purpose is to make it easy to tell how much Windex is left in the bottle.
I’m sure they do it partly to assure customers they are receiving something more than water. In that same regard, it’s an indication that it should not be consumed internally.
There is a clear Windex. I think it’s supposed to be their “green” product.
Before all the blue drinks such as Gatorade, the blue in Windex and in washer fluid was supposed to be a “do not drink” warning. Now, not so much.
I dunno if this is relevant, but looks like a good place to make this comment - I was in a Dollar Store some years ago and was horrified to see blue cleaning products on the shelf in what looked EXACTLY like soda bottles. Made in China, of course. At least the liquid was blue, though some kid could have gulped it down thinking, ‘cool, blue soda’.
The blue color has no function for cleaning. Same reason that there is color in automotive windshield washer, antifreeze, and Mountain Dew. So you know it isn’t just water.
I buy Windex Multi-Surface and it is clear.
Since the OP’s question has been answered, reading this thread reminded me of an episode of “Scrubs” where the janitor put blue gatorade in his squirt bottle, then proceeded to spray it in his mouth and weird people out.
Great episode.
/end off topic nostalgia 
There’s a line of Mexican products called Fabuloso that are also in beverage-style bottles. I am amazed that legions of children don’t get sick every year from drinking it.
Indeed… a little poking around and sure enough, people are drinking it. Happily, it’s apparently more a bad-tasting beverage than a strong and effective cleanser.
To take it a step further, some friends of mine filled an old dish washing soap bottle with sugar syrup (for consistency) and a bit of green dye (and some rhum), and went around drinking from it. Very amusing.
Another answer is to differentiate it from other cleaning chemicals that the cleaner/janitor may be using.
In general, Blue = Glass Cleaner, Green = Disinfectant, Red/Purple = Multipurpose Cleaner, etc…
Although with the new clean and green chemicals this is no longer the case.
This reminds me of a story about my mo-inlaw while she was at home in her elder years:
Her son asked her if she had anything to drink in the 'fridge and she said there was some orange soda that tasted terrible. He could try that and if he liked it he could take it home with him. He opened the 'fridge and said “Mom, this is orange-glo floor cleaner”. :eek:
To make it… “PURTY”… “Dang, that winder stuff, shore is purty!” <hyuck…hyuck>:D