confused with this strange doubt

abc is my login id

ls -l | grep abc
drwxr-xr-x 13 abc req 1024 Jun 21 22:50 abc

i just reset my group from req to try by changing the entry in /etc/passwd

but still
ls -l | grep abc
drwxr-xr-x 13 abc req 1024 Jun 21 22:50 abc
instead of try

strange thing is i have a program that would execute only if the group is try and now i am able to execute that (seems grp has been changed but i couldnt reflect the change in /users/ )

what could be the reason?

hope i make things clear