Recently, my mother told me a story of myself as a child. When strangers approached me and said things such as: "Isn’t she lovely?" or "What pretty hair you have!" I would innocently answer: "I know".

My unassuming arrogance would take people aback, then everyone would laugh at the adorable curly-haired prima donna, enough to assuage my mother's embarrassment. It would be easy to dismiss my younger self as a smug, precocious little brat, but it really just showed that when a child hears something enough times, they accept it as merely another fact of life.

As I grew older, I began to realise there were other factors at play, which made me uncomfortable.

Many of these compliments came from white women, but the majority came from black women, inside and outside of my own family. I was light-skinned with long thick hair thanks in part to my father's white English heritage. That was all that qualified me to be considered "beautiful".

It had nothing to do with being funny or smart but plenty to do with physical attributes over which I had no control. The confidence I had displayed as a young girl became insecurity then anger. I didn't want preferential treatment because of something as superficial as skin colour or hair texture. My mother, the first woman I ever knew, loved and admired, was a dark-skinned black woman and, to me, the epitome of beauty and glamour. What was the big deal?

And then I realised and checked my own degree of privilege – it is far easier to resent one’s own skin for giving you advantages you haven’t earned than despising it for what it takes away.

Darker skinned women and, yes, men too, face that reality – an issue brought to the fore in the documentary Dark Girls, directed by Bill Duke, premiered in the UK last week.

Focusing primarily on African American women, the film opens up the conversation of colourism – a shameful discrimination generally against your own community on the basis of skin colour.

It is a legacy of slavery and plantation society that placed white slave-owners at the top of the top of the social ladder, followed by those who were mixed race/lighter skinned (who were given work in the house, with the added bonus of being a plaything for the massa, wahey!), with darker skinned black men and women (who were also raped – hence, the light-skinned house slaves) at the bottom of the pile doing the back-breaking labour in the cotton fields.

While the physical chains of bondage may be broken, for many in the black and Asian community, colourism is still a part of life – a psychological prison of self-loathing and envy. Comments such as, “You’re pretty ... for a dark skinned girl” or “I hope the baby comes out light” are par for the course.

Type dark skin or light skin into Twitter and you will seecolourismin action. One tweet: "Party on Friday. White Girls free. Light skin girls 5dollars. 50 dollars for dark skin girls". Another: "I thought cute dark skin girls with long hair was a myth ... I feel like I seen big foot." (sic) Within the past week, ‘dark-sinned vs light-skinned’ has been a trending topic. As one angry tweeter kindly pointed out, "Is this what Martin Luther King died for?"

Dark Girls makes for a haunting and uncomfortable watch. Listening to beautiful women admit to insecurities thatled them to request bleach in their bath water or putting hair removal cream in the scalps of their light-skinned school peers as an act of jealousy would seem all but ridiculous if it didn’t hit so close to home.

It features men with pixelated faces trying and failing miserably to justify their own prejudices – "I just prefer light skin women". "Dark skinned women just look wrong next me" –to stories from African American women confessing black men would lust after them in private, but opt for a light skinned trophy to parade in public.

Some find it bemusing that journalists, feminists and social commentators devote so much time to discussing the politics of hair texture and skincolour but it is absolutely, unequivocally, political.

Based on these personal accounts, is it a coincidence that 50 per cent of all Black Caribbean men in Britain have partners outside their own race? Or that the majority of high-profile black men– from politicians to sport stars – have a white partner? Are they simply exercising their right to choose, or attempting to exorcise their own demons?

In the Caribbean, such as the Bahamas where I was born, the minority light skinned community forms the majority of the ruling elite – the effects of generations of wealth and privilege and marrying the ‘right’ people from the ‘right’ (and light!) families.

The ugly truth is while racism – whether institutional, structural or ingrained – and inequality persists, so will colourism. It is no surprise that skin bleaching creams are most popular in developing countries.

According to the World Health Organisation (WHO), 77 per cent of Nigerian women use them. In India – home to a third of the world’s poorest people – two thirds of all skin products contain lightening agents. For some, lighter skin is seen as a route out of poverty, creating opportunities to cheat a system engineered to oppress. It South Africa, it is the difference between being black and part of the ‘coloured’ middle class.

The women featured in Dark Girls weren’t born hating their skin, they hated the limited social outcomes it extended, the way they were treated and spoken to because of it. But while colourism differentiates, racism does not. Being mixed didn’t prevent me from being called a P*ki or a n*gger while growing up in the north east. We are all dark girls.

Perhaps one of the most heart-wrenching moments of the documentary is its opening; when a beautiful cherubbarely five years old, cannot meet the camera’s gaze as she admits to hating being called black.

I hope that by having these conversations and confronting the enemy within, as well as the bigger picture, little black girls of any skin tone won’t ever have to question their looks. Society will learn to tell them they are beautiful, and their response, quite rightly, will be: “I know”.