Color
Color, also known as gamma decay or DgammaDtime, was a third-order options Greek measuring the rate of change of gamma with respect to time, indicating how much the gamma of an option was expected to change as each calendar day passed, even if the underlying price remained constant.
Color occupied the same conceptual position for gamma that charm occupied for delta. While charm described how delta drifted over time independently of price moves, color described how gamma itself evolved with the passage of time. Understanding color was essential for participants who managed large short-gamma or long-gamma books across the NSE's weekly expiry cycle, where the passage of just one or two days could materially alter the gamma profile of the entire position.
For near-expiry ATM options, color was typically negative — gamma increased in magnitude as expiry approached, meaning gamma became larger (more negative for short-gamma positions) over time. This was the well-known phenomenon of gamma explosion near expiry: in the final days before a weekly NSE expiry, ATM options accumulated extremely large gamma values because each point of underlying movement caused a disproportionate change in delta. Color captured the daily rate at which this gamma expansion was occurring.
The practical implication for short-gamma options sellers on NSE's weekly cycle was straightforward: a position that appeared to have manageable gamma on Monday became potentially dangerous by Wednesday or Thursday as color accelerated the gamma growth. A trader who sold an ATM straddle on Nifty at the Monday open and ignored color would be surprised by how much more sensitive their position had become by Wednesday, even if Nifty had barely moved. The delta hedging requirement grew proportionally with the expanding gamma, and failure to account for color led to under-hedging.
Conversely, long-gamma traders who bought straddles or strangles benefited from positive color near expiry — their long options gained gamma (and therefore scalping opportunities) automatically as the expiry approached, even in the absence of price movement. This time-driven gamma enrichment was part of the appeal of long-gamma positions in the final sessions before an NSE weekly expiry.
Color was a third-order Greek and was not displayed on standard retail platforms. Its value was expressed in terms of gamma change per calendar day. Institutional options desks incorporated color into their end-of-day risk reports to project the next day's gamma profile, allowing preemptive hedge adjustments rather than reactive ones. For NSE options where weekly expiries created a rapid gamma lifecycle from Monday to Thursday, color was a genuinely material risk measurement tool.