Which Online Game Has a Green Trail and Pink Snakes Like Snake? Slither.io

You're describing Slither.io (2016, by Steve Howse).

Why It Matches

• Green Trail: Your snake leaves a glowing green (or custom-color) trail as it moves.
• Pink Opponents: Other players' snakes appear in various colors; pink is a common default/spawn hue.
• Snake Mechanics: Eat orbs → grow longer → avoid head-on collisions with other snakes (your head hits their body = you explode into orbs).
• Browser & Mobile: Play free at slither.io or via iOS/Android apps.

Similar .io Games

• Agar.io – Cells eating cells.
• Wormate.io – Worms with power-ups.
• Little Big Snake – Quest-based progression.

If the game was 3D or had distinct "teams," it might be Snake.io or a Snake Battle variant, but Slither.io is the iconic green-trail/pink-snake match.