If a brown mixture becomes too cool while making warm brown, what should be increased?

Correct answer: A little red-orange

Colour temperature describes whether a colour appears warmer or cooler. Red-orange contributes warm, reddish energy to a brown mixture, so adding it in a small amount can counter excessive blue or green influence. The change should be gradual because a large addition may overpower the mixture. Thus option A is correct. More blue or blue-green would make the brown cooler, while black mainly reduces lightness rather than warming it.