How to change the font in LineLegend?

Question

Is it possible to change the font in LineLegend? In fact, I need a mathematical font (like Times) in this part.

Answer 1

You can use the option LabelStyle with suboptions FontFamily, FontSize, FontColor etc to set font properties:

LineLegend[{Red, Green, Blue}, {"red", "green", "blue"}, 
 LegendLabel -> Style["legend", FontFamily -> "Arial", 32, Black], 
 LabelStyle -> {FontFamily -> "Times New Roman", FontSize -> 24, 
   FontColor -> Purple, FontSlant -> Italic, FontWeight -> "Heavy"}]

For the options FontSize, FontColor, FontSlant, FontWeight, Wolfram language is able to infer the associated option if you provide only the values of these options:

LineLegend[{Red, Green, Blue}, {"red", "green", "blue"}, 
 LegendLabel -> Style["legend", FontFamily -> "Arial", 32, Black], 
 LabelStyle -> {FontFamily -> "Times New Roman", 24, Purple, Italic, Bold}]

same picture