One of the subtlest ways the message is secretly conveyed in Bridgerton is in the way Penelope Featherington dresses and also in the unconscious reactions of her and her family to her dresses.
For much of Bridgerton’s first season, Penelope dresses in yellow and at one point makes an exasperated joke about it, like she hates the choice of color, but actually hides a loaded secret meaning.
Her outfits also act as an unconscious secret revelation in Bridgerton of the truth of Lady Whistledown, because Penelope’s choice of yellow offers insight for those familiar with Regency fashions.
Yellow was actually the most fashionable color of the Regency era and the idea of Penelope being forced to wear it by her alien mother fits the often comical misfit status of the Featheringtons in Bridgerton.
It is unclear if her ignorance of this fact is intentional, but it is telling that it is her family that chooses him for her in Bridgerton, pointing out as unaware of the true mark of good taste.
Since Lady Whistledown is the self-proclaimed model of virtue, taste, and fashion, it is fitting that she is frequently seen in yellow as a subtle indicator at Bridgerton.
Beyond that, yellow has symbolic connotations that fit Penelope’s secret double life in Bridgerton. Color is associated as much with deception and jealousy as it is with new life, intellect, and enlightenment.
Yellow’s association with creativity, her vigilance of the high society artistic subculture that is so tied to self-expression and individualism is the biggest limit to that kind of welcoming culture she welcomes as Penelope in Bridgerton.