Adult Eastern Green Lizards (Lacerta viridis; eastern Europe), Western Green Lizards (Lacerta bilineata; western Europe) and Balkan Green Lizards (Lacerta trilineata) are very difficult to distinguish in places where their ranges overlap.
Usually, adult Balkan Green Lizards have yellow throat markings and adult Western and Eastern Green Lizards have blue throat markings.
Immature Balkan Green Lizards are easily distinguished from immature Western and Eastern Green Lizards by the number of stripes running down their backs: Balkan Green Lizards have 3 or 5 stripes, while Western and Eastern Green Lizards have either 2 or 4 stripes.
There is an ongoing discussion as to whether Lacerta viridis and Lacerta bilineata are separate species.

Near the Rozhen Monastery, Melnik, Bulgaria, 28 July 2017