Which mixture can change colour temperature without greatly changing its value?

Correct answer: Add a warm or cool colour of similar value

The governing concepts are colour temperature and value. To shift a colour warmer or cooler while keeping its lightness relatively stable, add a warm or cool pigment that has a similar value to the original mixture. This changes hue and temperature with less lightness change. Black lowers value, white raises it, and grey usually reduces saturation while also affecting the visual value, so those choices do not meet both conditions as precisely.