Here's the earth in perspective. See that globe in the corner of the classroom? It's probably a foot, maybe two feet in diameter. The earth's atmosphere scaled down to that size would be as thin as the skin of an onion. Now you tell me that if anyone was out there in space looking back on the earth to the same scale, they would be able to see the "blue" of the atmosphere? I think not. (BTY I'm not being facetious here just factual). However, the earth's atmosphere does make its color apparent at certain locations and times. During a lunar eclipse, we see the moon not blackened but darkened with a ruddy haze. This is caused by sunlight refracting through earth's atmosphere. If you were on the moon during that eclipse and look back at the earth, you'd see the dark side of the earth surrounded by a reddish glow.********Addition****** The color of liquid water does have a blue tint to it. And the deeper the body of water, the deeper that tint gets. Also, earth is also called the Blue Planet because of the color of its water as seen from space, not its atmosphere.
I teach physics, too.