Which combination of colour is the most convenient

Solution

Red and green is the most convenient combination during day and night time because of very precise visibility. In modem colour theory, also known as the RGB colour model, red, green and blue are additive primary colours. Red, green and blue light combined together makes white light, and these three colours, combined in different mixtures, can produce almost any colour. This is the principle used to make the colours on computer screen and television.