Shrewd Hatchling

Shrewd Hatchling enters with four -1/-1 counters on it.
{U/R}: Target creature can't block Shrewd Hatchling this turn.
Whenever you cast a blue spell, remove a -1/-1 counter from Shrewd Hatchling.
Whenever you cast a red spell, remove a -1/-1 counter from Shrewd Hatchling.

The List

Modern Masters 2015

Shrewd Hatchling enters the battlefield with four -1/-1 counters on it.
{UR}: Target creature can't block Shrewd Hatchling this turn.
Whenever you cast a blue spell, remove a -1/-1 counter from Shrewd Hatchling.
Whenever you cast a red spell, remove a -1/-1 counter from Shrewd Hatchling.

Duel Decks: Izzet vs. Golgari

Eventide

Shrewd Hatchling comes into play with four -1/-1 counters on it.
{UR}: Target creature can't block Shrewd Hatchling this turn.
Whenever you play a blue spell, remove a -1/-1 counter from Shrewd Hatchling.
Whenever you play a red spell, remove a -1/-1 counter from Shrewd Hatchling.

If there are no -1/-1 counters on it when the triggered ability resolves, the ability does nothing. There is no penalty for not being able to remove a counter.

If you cast a spell that’s both of the listed colors, both abilities will trigger. You’ll remove a total of two -1/-1 counters from the Hatchling.