What are these strips on HAL Tejas?
Fin and Tail formation lights.





Look up slime lights. When lit, they look like slimy green, hence the name. They are used for flying formation at night when it isn't possible to use visual clues such as wingtips, missiles, intakes, etc. Basically for dark/night visual pickup, formation keeping. They are for night operations and have visible and infrared modes (for use with NODs).