For all the revelations in Oprah Winfrey's interview with Harry and Meghan, the Duke and Duchess of Sussex, the most striking was Meghan's claim that an unnamed member of the Royal Family raised concerns and questions about the skin colour of her then-unborn son, Archie. Black Americans winced at that, recognising, even in those royal and foreign circumstances, a version of the same anti-Black racism and colourism that we have long faced.

The accusation was yet another confirmation of the truth that no matter how high you rise in life or how noble your parents are, the shade of your Black skin may determine your value to others in the world.

When Meghan and Harry announced the birth of their son, no one, not even the Royal Family, could deny his African-American heritage. His mother, after all, is a biracial woman, born to a Black mother and a White father. What seemed to be at issue for someone in the Royal Family was something more sinister — just how dark-skinned the mixed-race child might be.

Their question was perhaps rooted in an understanding that the alchemy of genes can make the shade of a child's skin unpredictable. I know that all too well. As a Black person of mixed race, I appear White to the world. My siblings, who are Black, have given birth to their own multiracial children who fall across a colour spectrum. Even within my siblings' individual families, there is variation. My niece, who has honey skin and blue eyes, has two brothers who are chocolate brown. My nephew with the square jaw, muscular build and colouring of Prince William has a sister with the skin tone and eye colour of Meghan.

Black folks have long used a rhyme penned by the blues singer Big Bill Broonzy more than 60 years ago to remind themselves about colourism: "If you are White, you're all right, if you're Brown, stick around, but if you're Black, get back."

Those of us with lighter-skinned or mixed-race children have our own examples of people appraising them and determining their value. We have felt the shame of having people comment about a child's "nice summer tan" complexion, "good hair" or "bright eyes".

Black people also understand that the shades of our Black faces can determine our outcomes in life, not least of all because White people — common and royal alike — are so sensitive to our many hues. The writer David Dennis has for years challenged the Black community to acknowledge that even the racial oppression light-skinned Black people receive may differ by degrees. As he has long noted, lighter skin affects things from public perception to job prospects and even prison sentences.

This is hardly a new concern. Lighter-skinned Blacks or "mulattoes" were afforded preferential treatment during the era of slavery. Afterward, and throughout the early 20th century, the "one-drop rule" was used to assert that anyone with one drop of Black blood from an ancestor would be Black. That determination affected their legal and social status. And even in the Black community, there have been times when special privileges, if not rights, were denied based on skin colour.

The "paper bag test" was well known among Blacks in certain circles well into the 1950s. To pass the test — and gain invitations to social groups, nightclubs and even churches — your skin tone needed to be no darker than a paper bag.

While this type of blatant discrimination or social sorting is in the past, we know that colourism persists in the public consciousness. In America, the Black is Beautiful movement of the 1960s and 1970s helped the fashion, advertising and media industries reconsider the standards of Black beauty. Yet, even today, depictions of interracial families in advertisements for insurance, mortgages, laundry detergent and cereal overwhelmingly show mixed-race children with light-brown-sugar skin, loose, curly hair and thinner features.

And yet none of this means that lighter-skinned people escape scrutiny, even if they can move through some spaces with greater ease in some circumstances. To the contrary, the whole system of evaluation is an effect of the endless, ongoing reduction of Black people to the mere fact of their Blackness. It becomes a way of disciplining all of us, of tacitly legitimising the boundaries that society draws around us.

The alleged royal speculation about Archie's skin never implied that he would fit in just fine if he could pass for White. To the contrary, the mere fact of the question was a way of saying that he would always be subject to inspection, to the cataloguing and criticism of his fundamental difference from those close to the throne and the power it represents.

As a former actress, Meghan has commented about how the entertainment industry tried to lighten and brighten her image to make her more appealing to audiences. Nevertheless, in the interview, she suggested that she naively believed that her marriage to Harry and the birth of their son would demonstrate meaningful representation to people across the entire British Commonwealth who are predominantly people of colour. As an American, she also probably was aware that she was an important symbol to Black Americans who watched her break a racial boundary by joining the Royal Family.

Now that she and Harry have stepped away from their duties and almost all of their titles, it seems clear that the Royal Family have little to no interest in celebrating inclusion — let alone in actively encouraging it.

Still, in her bold willingness to challenge the royals by speaking out about her experiences with racism and colourism, Meghan reminds us that even in our increasingly multiracial and multicultural world — a world where Black people have joined Whites in reaching the pinnacles of power in politics, business and entertainment — there are still some places off limits to those who do not pass a certain test. And even those who do pass will be put on notice by the mere fact that they were tested at all.

• Steve Majors is a non-profit communicator and writer who lives in Takoma Park, Maryland. His book, High Yella, will be published in the autumn of 2021