The term red means ??? The term free indicates that the pilot is not currently involved in offensive or defensive maneuvers.
<embedded-cs-exch> = <yourcs> <mycs> | <mycs>
<ack> = [<mycs>] roger [<yourcs>]
<req-ws> = {check | say} weapon status
<sup-ws> = [weapon status [is]] red and free
Usually the pilot (P) requests weapons status from the E2 (E), leading to a simple request-reply-acknowledge interchange:
P: <embedded-cs-exch> <req-ws>
E: {<ack> | <embedded-cs-exch>} <sup-ws>
P: <ack>
Less frequently, the E2 may offer the weapons status, as in:
E: <embedded-cs-exch> <sup-ws>
P: <ack>