of ser and estar lays in the duration of the state that
is talked about.
Las fresas son rojas.= Strawberries are red. They are usually
and always red. However, if the state is only temporary
and it is to be expected that it changes eventually then estar is
to be used:
Las fresas están verdes todavía! = The strawberries are still green! But it is to be
expected that they will turn red eventually and
then they are perfect strawberries that are red as they
are supposed to be.
the meaning changes depending on whether ser or
estar is used:
= Pepe is a boring person.
Pepe está aburrido.
= Pepe is bored.
chico es listo.= The boy is clever.
El chico está listo.
= The boy is ready.
es una persona alegre.= He is a happy person.
De momento está alegre. = He is happy
(at least at the moment, you
never know about tomorrow! And it's not said
whether he is a happy person or not.)
es muy divertida.
= She is funny.
Ella está muy divertida.= She's in a good mood, she's having fun.