The key to drying leather effectively is air-circulation (not heat as it will cause cracking) so for example the bottom of a wardrobe or under the bed are not a good places. The reason they're turning green is because they didn't dry out properly and are now mouldy. Get saddle-soap (preferably lanolin-enriched) in a good shoe / leather-goods shop and follow the instructions. They'll probably need 2 / 3 treatments with a drying period in between to get rid of the mould. This is a cleaning / feeding process, then use dubbin for water protection.