The "Tomato/GFP-FLP/FRT" method can be used to generate mitotic clones in the eye with normal and mutant photoreceptor cells expressing different fluorescent markers. The method was described in
Gambis, A., Dourlen, P., Steller, H., Mollereau, B. (2011). Two-color in vivo imaging of photoreceptor apoptosis and development in Drosophila. Dev. Biol. 351(1): 128--134.
A database is available showing the effects of many defined mutations on photoreceptor development.