It depends what type of finch you are talking about, there are hundreds of different ones.
With the most commonly kept finch, the zebra finch, the male has orange cheek patches and chestnut flanks with white spots, while the female does not (in more mutations). Males have red beaks and females have orange beaks.
Gouldian finches have a few differences, but males have a lot more blue on the back of their neck compared to females.
I think most finches you can't accurately tell apart visually, they need DNA sexing to be completely sure.
Google the type of finch you are thinking about for information about the difference between males and females.
With the most commonly kept finch, the zebra finch, the male has orange cheek patches and chestnut flanks with white spots, while the female does not (in more mutations). Males have red beaks and females have orange beaks.
Gouldian finches have a few differences, but males have a lot more blue on the back of their neck compared to females.
I think most finches you can't accurately tell apart visually, they need DNA sexing to be completely sure.
Google the type of finch you are thinking about for information about the difference between males and females.