Abstract: Warming your flash will greatly improve skin tones. Which warming gel you use depends on your subject, the lighting environment, your camera's color palette and personal preference.
I still remember the day I was introduced to warming gels. It was nearly 30 years ago. I was assisting photographer Chris Usher in 1988 on a shoot in Washington for Businessweek. As he was setting up his light he asked me to hand him his gels, absentmindedly muttering, "Always gotta warm the key light…"