Y Not?" asked the front page of Women's Wear Daily the morning after last week's Gucci show in Milan.

"Frida Giannini's leading Gucci into its tenth decade with a feisty collection and a strong tribute to Yves Saint Laurent." And Giannini is not the only designer to have referenced this great French name. Miuccia Prada, too, came up with a typically idiosyncratic take on the Saint Laurent Mondrian dress – that short, sharp, symbol of modernism – in her collection, "Prada loves Yves Saint Laurent", and has never made excuses for that.

In a world where our fashion knowledge is such that the more obscure a source used by a designer, the better, looking to the Yves Saint Laurent archive for inspiration is the exception that proves the rule. Following a retrospective exhibition of his work in Paris last year, it came as no surprise that the spring collections are awash with surprising colour juxtapositions – Saint Laurent was 20th-century fashion's great colourist and everyone from Raf Simons to Marc Jacobs and from Prada (again) to, of course, Stefano Pilati, today the creative force behind the brand that still bears his name, is indebted to that aspect of his work.

For the forthcoming autumn, and the two aforementioned homages aside, there's more generally a strictness and a sense of repressed sexuality on the agenda that is pure Belle de Jour by nature – Saint Laurent dressed Catherine Deneuve as the grande bourgeoise prostitute in the Bunuel film. The S&M sexual overtones to Helmut Newton's photographs of the designer's work are a part of the story, too.

There are only very few fashion talents great enough that even the most forward-thinking names are prepared to acknowledge their influence, and Saint Laurent is perhaps the most oft-cited of them all. Simons says he carries the Saint Laurent heritage around with him "like luggage". And in this case, imitation really is the most sincere form of flattery. There is, after all, not a single day when a woman reaching into her wardrobe isn't somehow touched by his signature. Black turtlenecks, leather biker jackets, tailored trouser suits for women, pencil skirts... all were hallmarks of his extraordinary output. It's small wonder then that neither is there a designer arrogant enough not to acknowledge that fact.