This value is driven eastward by the change direction of this IV, that is, after you bought the call option, it was positive, and when you sold the call option, it was negative.
Similarly, it is positive when buying put options and negative when selling call options. Buying options means buying volatility, and selling options means selling volatility.
In short, the vega values of call options and put options are positive, the vega values of call options are positive and the vega values of put options are negative.
For example:
If the vega value of the option with the value of 100 is 7.5, if the volatility of the underlying asset price increases by 1%, the value of the option will increase by 7.5, reaching 175. Obviously, when the volatility of the underlying asset price changes, the option value will also change in the same direction.
Factors affecting Vega
In addition to the volatility mentioned above, if the change of vega value is affected, there are three main reasons, namely: the influence of real value, flat value and imaginary value options on Vega; IV's influence on Vega; Effect of expiration time on Vega.