Was the BrEng term "coloured" derogatory in the 1970s?

SAM
Look... I owe it to myself to say this to you, okay? Leave Tony Crane. Just go far away from him. He's gonna ask you to marry him and he's gonna make you a business partner.

EVE
Is that what this is all about? Does it bother you that much? A coloured bird with a bit of power?

^{BBC One's Life on Mars series 2, episode 1}

For those who have not watched the BBC TV series a very brief synopsis:
After an accident, Sam Tyler a Detective Chief Inspector in 2006, wakes up in 1973. Now a detective inspector, he has a love-hate relationship with DCI Gene Hunt—one of the most politically incorrect characters in the history of British television. Sam Tyler doesn't know if he's mad, in a coma or if he's travelled back in time. All he wants is to go back home to the future.

In view of the fact that the TV series is set in 1973, a time when sexism, racism, and homophobia was rife and the British general public had only started condemning those acts of behaviour. I was taken aback to hear the following lines:
Does it bother you that much? A coloured bird with a bit of power?

I was only ten years old in 1976 and I remember the noun Black (or adjective black) was considered derogatory, almost a taboo, whereas coloured was the "polite" term used to describe anyone whose skin was dark-coloured. But childhood memories can play tricks, so I'm not absolutely certain.

Was the term coloured derogatory in the 1970s? Did Eve call herself "coloured" because she knew it was offensive or did British black people call themselves that?

Nowadays, I know it's the other way round, and I'm pretty sure that Benedict Cumberbatch does too. But what about the 1970s? Shouldn't the actress line have been:

Does it bother you that much? A black bird with a bit of power?

Thinking back, I believe coloured was originally a euphemism, used to avoid the word black which British people thought, probably correctly at the time, was offensive.

I believe the demise of coloured as an acceptable term dates from the emergence of black, mainly from the American black community, as a term of pride. With the growth in the use of black, I think coloured came to be seen, by some people (not all), as a patronising slur, a 'kind' way of not referring to a person's blackness, treating the fact as though it were a handicap.

In this context, I think Eve was deliberately using derogatory terms. She's expressing her perception of Sam's point of view, so she uses language that reflects what she thinks he thinks of women and blacks.

Based on my recollection of the 80s and 90s in a white to multicultural bit of London I would say "not really". There were certainly white people who objected but they were progressive, even hippie-ish types in other ways.