The left photo by the Brazilian photographer Jose Reynaldo da Fonseca was shot with flash which reveals some colors. You can find the it here and read what Jose wrote:
"A transparent butterfly. The detail here is that I didn't use flash, I got but I had to use 1/50 with f/2, without tripod... the one that the times don't help in details. Usually the transparent wings with the light of the flash give some reflexes iridescent hue, which a lot of people find strange!"
"Greta oto is one of a number of similar transparent winged butterflies. It comes from central America, and is found from Mexico to Panama. It is quite common in its zone, but it not easy to find because of its transparent wings, which is a natural camouflage mechanism.'
The right picture is the same butterfly shot without flash. As some people are thinking this is fake here you have the link for Wikipedia.