You cannot customise each eye individually.

[DiamondAurumFox]

The MOST glaring issue of this wonderful applet is that, you can customised the shape and the colour of the eyes, but not each eye individually. This limitation makes it impossibly to the eyes to look like the Twins from Terraria

[luisbocanegra]

That would require a bit of refactoring as there can be up to 9 eyes but I think it can be done. I will keep this into consideration for future versions.