Tandy leather has some great leather products. I use their Dr. Jackson's Leather conditioner. Actually smells like new leather.
Their stores also carry finished leather sheets that match the GT perfectly. At surprisingly minimal cost. You could just recover your kick panel.
The color on leather seats and couches is actually paint like and not a dye. Tandy carries dye not the paint. Although the dye will work for touch up as mentioned by Art138. You can get the leather spray paint at shoe and boot repair shops. Also on line. The product is called Moneysworth & Best Brillo Leather Coloring. Auto paint stores have the same product sold under the SEM brand although fewer color choices. This also works great on leather couches, use two colors to match the modeled look.