BarLegend

BarLegend[cf] generates a legend that identifies colors from the color function cf with an automatic range of values.

BarLegend[{cf, {min, max}}] generates a legend that identifies colors from the color function cf with the range of values between min and max.

Examples

Create a color bar legend:

BarLegend["Rainbow"]

With specified range:

BarLegend[{"TemperatureMap", {0, 100}}]

Please visit the official Wolfram Language Reference for more details.