Chromesthesia
Also known at Sound-Color synesthesia, Chromesthesia is when the synesthete's brain triggers colors when sounds are heard. Some may actually see the colors in front of them when a sound is heard, like if someone is hammering a nail into a wooden board, the synesthete might see blue dots in front of their eyes. Some only see the colors in their minds. But it really depends on the person. Like with any other type of synesthesia, each sound heard can trigger the colors for as long as they last, or it might linger in the air for others for a bit.