Asr time will remain until sunset. However, it is Makrooh (undesirable) to offer Asr Salaat when the colour of the sun changes and the sun’s rays change to yellow.
If due to some reason one gets delayed, Salaat in this Makrooh time should be offered and not allowed to be missed. In future, it should not be delayed.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai