Get a very small paint brush and just block out the horses,let that dry , do it again and let it dry then dye the entire concho, leave the dye on for thirty seconds then wipe the entire concho with a damp sponge very lightly.
You'll see the horses better.
Instead of the eyes maybe you could just put one on the concho as a birth stone if you have different colors.
Check this link ...
http://www.tandyleatherfactory.com/Resisting-Techniques/Resisting-Techniques.aspx