So to summarize all of the varying opinions -

Some think it's ok to be called "blue".
Some don't like it but tolerate it.
Some say it's a sign of disrespect, others say not.
It appears to be more disrespectful at higher levels than lower levels.
In at least one California association, it's an absolute no-no.

Same applies to the word coach, especially when the "head" coach is actually the Manager.

If I offended anyone, that was not my intent so I extend my apologies.

To everybody - go out and have good games wherever they are and whatever the level.