Question

Flexibility is a key component in adapting to each new challenge: most students can do this by the end of week one.

Is this sentence right? Should the colon actually be a semicolon?

Answer 1

If the sentence after the colon is a detail or explanation for the sentence before the colon, then the colon is correct. Also, the M on "most" needs to be a capital letter.

http://grammar.ccc.commnet.edu/grammar/marks/colon.htm

If they are intended as closely connected sentences (too closely connected to be two separate sentences), but not one as the furtherance of the other, then a semicolon would be correct.