I'm sorry, I have to disagree with you.
The sky looks blue to us, because the earth's atmosphere breaks the light emitted by our solar system's central luminary - the sun - and the spectrum of light that reaches the earth's surface is interpreted by our brains as what we know as the color of blue.
The growth of grass can be experienced empirical, measuring the length of the same blade of grass in to distinct points of time.
And the third question depends on what you define as sand. If you mean by it naturally occurring, unsolidated sedimentary rock having a grain size between 0.063 mm and 2 mm, then yes: There is sand in the desert.

Sry, I watched 2 season of The Big Bang Theory the last 2 days. It kind of influenced me.
Btw: Call me Sheldor the Conqueror...