When you are speaking of a property something has, like for example, colour, you use "ser". I.e: "El edificio es blanco" If it is a property of an object that changes easily or changes all the time, like the STATE of traffic lights, then you use "Estar". I.e. "El semaforo esta en rojo" Like in Andy's example, "Sometimes I am a little bit selfish" , 'I AM' translates directly to 'Yo soy' and that's why we say "A veces soy un poco egoista". When it comes to people it does become a bit irregular, speaking about emotions and properties that describe us, we use "ser" and "estar" the same as with objects: "Estoy feliz", "Estoy emocionado", "Soy alto", "Soy delgado". But when speaking about behavior or situation (like being rich) we always use "Ser": "Soy rico", "Soy bueno", "Soy egoista". Hope my explanation is clear enough and will help you with that tricky bit of Spanish. If not, I'll review it when I get on my PC and format it properly too! Feel free to PM me with your questions, I'll try to answer ASAP :3 Buen día!

As a fellow Spanish learner I just want to chime in and say that it's important not to take the "intrinsic" versus "temporary" rule for ser vs estar too literally. It's a decent rule of thumb but it often fails. The classic example: "Él está muerto". Nothing temporary about that! There are also many adjectives describing emotions that take "ser" like "feliz". If you like linguistics, you may find this Wikipedia article interesting: https://en.wikipedia.org/wiki/Romance_copula The takeaway is that the choice of ser vs estar tends to reflect etymology rather than abstract meaning.

I would say: nuestro coche fue azul. Estaba just doesn't sound right. ejemplo: Ayer nuestro coche fue azul pero cambiamos el color y hoy es rojo. I had a question once about when a person is poor in Latin America. Do we use ser or estar. In the US maybe we always think about the opportunity to rise in financial status. So, I asked a Mexican girl. Do we say: El hombre es pobre or do we say: El hombre esta pobre. "It's always, el hombre es pobre." she said. An unchangeable condition apparently in the mindset down south.

Era. Nuestro coche era azul.

The correct use of ser and estar can present many challenges for us Spanish learners. I once wrote a notebook entry in which I wanted to say "sometimes I am a little bit selfish" and I wrote "a veces estoy un poco egoísta". The entry received 5 corrections and everyone corrected it to "a veces soy un poco egoísta". It seemed odd to me that you can't use estar in this example, because I'm not a selfish person.