Iauto setting not replicable

Guys,

stupid question. i was trying to learn and try to use as much as possible the camera deciding the settings. By chance i take few pics using IAuto and i notice that the result in JPG are far better than what i can do and in addition i found impossible to replicate the results.

i've take two pics of the same subject and even if the settings (reading the info of the pics) were identical the colours were quite different.

do you know why?