In addition:
The fact that "красный" (red) meant "beautiful" in old slavic language can be noted if you look at word "прекрасный" ("very beautiful" literally).

There is fun fact about it: the famous Red Square in Moscow is not "Red" at all! In the old times there were no red bricks. That name meant/means "Beautiful Square".
It is fun, but even native russians do not know it often.