Nayani Thiyagarajah comes from a family taught to flee from the sun.

"For centuries we have hidden from it. It makes us darker. And in my culture, dark ain't lovely," says the Tamil filmmaker in her documentary Shadeism, which is currently finishing production and scheduled to be released in the fall.

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Her film is about a form of discrimination, not by one race against another, but by people of colour against each other.

Back in the 1980s, social scientists identified the tendency as colourism, describing a lower social status due to skin tone. And now, shadeism. The term may be more recent, but the practice continues to afflict the cultures of many people of colour.

In the '80s, I attended a memorial for the life of Dr. Martin Luther King, Jr. in Memphis, Tenn., when a slight mulatto pastor stepped to the microphone.

"Who is this little yellow preacher?" he asked the crowd, implying his skin tone somehow made him inadequate to speak to the legacy of Dr. King. The racial implication didn't seem to shock anyone in the mostly-black audience that night, except me.

In 1926, when blues artist Bessie Smith sang, "I'm as good as any woman in your town / I ain't no high yeller, I'm a deep color of brown," she was reflecting the bitter hierarchy of skin tone imposed by slavery, known as pigmentocracy.

As Ruth Fisher of the Understanding Slavery Initiative told the Guardian newspaper in 2011, "Generally speaking, on plantations, you had what you would call the house slaves and the field slaves. The delineation of shade in that regard would be those who were darker would be in the fields, while those who were fairer or of mixed heritage would be the house slaves.

"Part of it was because of the fear factor; those who were more closely associated with being African, or those who were new to the plantation, would be darker and more resistant than those who were born on the plantation, and therefore considered to be less aggressive, less rowdy."

Raised as a 'light-skinned wonder child'

The 26-year-old Thiyagarajah is from a Sri Lankan family unburdened by the legacy of American slavery, and yet it's arrived at a very similar place.

She was raised from birth as a "light-skinned wonder child," she said during an interview on The Sunday Edition airing this weekend.

"To this day, my family still reminisces about how light I was. But growing up, as I grew darker, I began questioning the notion of light skin being better. What did my family's constant commentary on my skin colour really mean? I began to wonder. If I wasn't light anymore, did that mean I was no longer beautiful?

"This is an issue of beauty, of old ideas that determine what is still beautiful. Of how the colour of our skin has and continues to affect how we view ourselves. This is shadeism."

Her documentary touches on the multi-billion dollar industry that's cropped up around skin-lightening cosmetics, fuelled in part by recent revelations the Cameroon pop singer Dencia is an enthusiastic client of one marketed as "Whitenicious."

It reportedly costs as much as $150 US for 60 ml. But in Asia, where the demand is enormous and such prices are beyond reach, some settle instead for more toxic and harmful chemical bleaches in the quest for a damaging beauty ideal.

Thiyagarajah says she was spurred to make the film after watching shadeism seize a new generation in the form of her four-year-old niece. You see the pair of them on screen as the child expresses her desire to be whiter, like the models in glossy magazines.

Those very magazines periodically inflame and inadvertently illuminate the business of shadeism.

One of them was said to have lightened the skin of the singer Beyonce for a L'Oreal ad. Actor Gabourey Sidibe got the same treatment from Elle magazine.

In 1994, Time Magazine admitted to darkening the skin of accused murderer O.J. Simpson, supposedly in the name of art, provoking immediate cries of racism.

'You're really lucky to be this black'

But now, there's a public debate about shadeism. At the February gala of Black Women in Hollywood, Lupita N'yongo, the Oscar-winning breakout star of 12 Years a Slave, read a fan letter she'd received from a young girl.

"I think you're really lucky to be this black but yet this successful in Hollywood overnight. I was just about to buy Dencia's Whitenicious cream to lighten my skin when you appeared on the world map and saved me."

"My heart bled a little when I read those words," N'yongo told the audience. "I remember a time when I too felt unbeautiful. I put on the TV and only saw pale skin. I got teased and taunted about my nightshaded skin.

"What is fundamentally beautiful is compassion. For yourself. And for those around you. That kind of beauty inflames the heart, and enchants the soul."

It may sound fanciful to a four-year-old taught from birth that her own society places a higher value on skin lighter than her own. But that is the barrier Nayani Thiyagarajah is also attempting to tear down.

(Listen to The Sunday Edition's conversation with Nayani Thiyagarajah when Rick MacInnes-Rae guest hosts on CBC Radio 1 on June 29 starting at 9 a.m. Eastern.)