Question: What modern system of a very old messaging method entails red and yellow ('Oscar') at sea, and white and blue ('Papa') on land?
Answer: semaphore communication
flag semaphore codes
semaphor
semaphore communications
semafore
semaphore comunication
flag semaphore code
semaphore flag signalling
semaphore flags
semaphore flag
semaphore
semaphone
japanese semaphore
semaphore alphabet
signaling semaphore procedure
shipping signals
flag semaphore
semifore