Color (or gamma decay) measures how an option’s gamma changes as time passes. It’s a higher-order Greek, and it’s the mathematical reason 0DTE gamma becomes so extreme into expiration.

What color captures

Gamma — the rate delta changes — isn’t constant over an option’s life. For at-the-money options, gamma rises sharply as expiration approaches, and color measures that increase per unit of time. It’s why an ATM option that’s calm with weeks to go becomes a hair-trigger on its final day.

Why it matters for 0DTE

Color is what makes 0DTE special and dangerous: as the clock runs down, ATM gamma spikes, so delta swings violently on small moves (a near-the-money 0DTE delta can jump from 0.2 to 0.8 on a modest move). This forces aggressive dealer hedging and amplifies intraday moves — the gamma feedback loop that defines 0DTE tape.

Color is time cranking up gamma. It’s why a sleepy option becomes a live wire on expiration day — and why 0DTE moves can be so sharp.

What it means for a scalper

You feel color every time a 0DTE option reacts explosively near the money late in the day. It explains the 3pm gamma effect and why sizing and stops matter more into the close. Part of the higher-order Greek family with speed and zomma.