Color

Color (also called gamma decay or DgammaDtime) measures the rate at which gamma changes as time passes, with all other factors held constant. It is a third-order Greek that captures how gamma evolves day by day as an option approaches expiration. If an ATM option has high gamma today, color tells you whether that gamma will be higher or lower tomorrow.

Why It Matters

Color is relevant for traders who manage gamma-heavy portfolios over multiple days. If you are long ATM options and relying on their gamma to generate profits from stock movement, color tells you how quickly that gamma will increase or decrease purely from time passing.

As expiration approaches, gamma concentrates dramatically around the ATM strike. Color quantifies this concentration. Market makers use color to anticipate how their gamma exposure will shift overnight and plan their hedging activity for the next trading day. For options sellers, color helps explain why gamma risk intensifies in the final days before expiration — an important consideration when deciding whether to hold a short option position into the last week.

How It Works

Color is the derivative of gamma with respect to time, or the third derivative of the option price with respect to the stock price and time.

How color behaves by moneyness:

• ATM options: Color is typically positive for ATM options as expiration approaches, meaning ATM gamma increases over time. This is the well-known "gamma spike" effect near expiration.
• OTM options: Color is typically negative for options that are meaningfully OTM. Their gamma decreases over time as the probability of reaching the strike diminishes.
• ITM options: Similar to OTM, gamma decreases over time for deep ITM options as their delta solidifies near 1.0.

Color and expiration dynamics: The most dramatic color effects occur in the final 5-10 days before expiration. An ATM option with 30 DTE might have a gamma of 0.03, but with 3 DTE that same ATM gamma could be 0.15 or higher. Color measures this daily increase.

Meanwhile, an option that is 5% OTM might see its gamma shrink from 0.02 at 30 DTE to nearly zero at 3 DTE. Color captures both of these opposing dynamics — gamma concentrating at the money and evaporating away from it.

Practical implications:

• If you buy ATM options to trade gamma, color tells you how much your gamma position strengthens each day
• If you sell near-expiration straddles, color warns you that gamma risk is growing daily
• If you hold OTM positions near expiration, color confirms that their gamma (and potential for large delta swings) is fading

Quick Example

You own an ATM straddle on stock RST at $100 with 10 days to expiration. The current gamma is 0.05 and color is +0.008 per day. This means:

• Today: gamma = 0.05
• Tomorrow: gamma = 0.058
• In 5 days: gamma = approximately 0.09

Your gamma is nearly doubling over the next 5 days purely from the passage of time. Each day, the stock needs to move less to generate the same dollar change in delta. This is great if the stock is moving — your gamma profits accelerate. But if you are short this straddle, the increasing gamma means your risk is escalating rapidly.

At the same time, an OTM $110 call might have color of -0.003 per day. Its gamma of 0.02 shrinks to 0.005 over those same 5 days, effectively becoming inert.