How do I make a colour warmer or cooler?

Warming or cooling a colour means rotating its hue slightly toward the warm (red/orange/yellow) or cool (blue/green/purple) part of the colour wheel, without necessarily changing its lightness or saturation much.

Practical advice

Adjust My Colour's 'warmer' and 'cooler' options do exactly this, and show the result at three strengths so a subtle or more pronounced shift can be compared directly.