Ghost yellow, Santa María, Colombia
Presumed sub species is Eurema albula marginella, which has a common name "White yellow":
...which explains why I could not find it in the "whites", it's a really light "yellow" insead.
''Eurema albula'', the ghost yellow, is a butterfly in the family Pieridae. It is found from southern Texas south through the West Indies and mainland tropical Central and South America to Brazil. The habitat consists of tropical forests and second growth.
The wingspan is 30–50 mm . Adults are pure white above with a black tip to forewing. Adults are on wing year round in the tropics. They feed on flower nectar.
The larvae feed on ''Cassia'' species .