This might help you

http://www.chelonia.org/sexing/sexing_Geochelone_carbonaria.htm

Your red foot should be greater than 6" long before determining their sex. You may be able to tell by the shape of the shell - Males have a figure of 8 and females are wider.

If you post a photo of your Tort (upside down) - someone might give you an opinion.

Hope this helps