I'm putting this online, so that it can also remind us what to look out for, when shooting these little Eurema lookalikes. This is taken from C&P4, but re-organised slightly to make it easier to make it understandeable.

Eurema species with no cell spots on the underside of the forewings
  • Eurema brigitta senna - Upperside forewing black apical border serrated but not more deeply excavated in spaces 2 & 3. Male has no brand.
Eurema species with one cell spot on the underside of the forewings
  • Eurema sari sodalis (Chocolate Grass Yellow) - Underside forewing apical area entirely dark brown.
  • Eurema andersonii andersonii - Underside forewing apical area not entirely darkened. Inner edge of black border in space 1a and 1b inclined slightly towards tornus. Upperside black distal border not more deeply excavated in space 2 than in space 3.
  • Eurema lacteola lacteola (Scarce Grass Yellow) - Inner edge of black border in space 1a and 1b inclined towards base. Upperside black distal border in space 2 more deeply excavated than in space 3. Female is greenish white.
  • Eurema tilaha nicevillei - Upperside forewing border continued along dorsum.
Eurema species with two cell spots on the underside of the forewings
  • Eurema hecabe contubernalis (Common Grass Yellow) - Upperside forewing black border in space 1a and 1b at right angles to dorsum or sloping towards base.
  • Eurema ada iona - Upperside forewing border below vein 2 cut away towards dorsum. Forewing apex rounded. Specimens usually smaller than 18mm
  • Eurema simulatrix tecmessa - Underside forewing has a large cleft reddish brown apical spot.
Eurema species with three cell spots on the underside of the forewings
  • Eurema blanda snelleni
I hope this helps a bit. I think I'll have to one day draw some diagrams to show where is what - especially the special names given to which parts of the wings.