09/09/2013 08:31 EDT | Updated 11/09/2013 05:12 EST

Derek Lam mixes his urban edge with a playful feel for spring at New York Fashion Week

NEW YORK, N.Y. - Derek Lam's clothes always have a pronounced urban edge. For his Spring 2014 collection, he wanted to be playful, too.

And so while Sunday's runway show at New York Fashion Week had some classic Lam elements, it also had unexpected nuances. For example, sparks of bright yellow, breaking up his usual crisp colour palette of black, white and navy. An elegant yellow crepe strapless gown came in sharp contrast to the series of bold plaids, in black and white or blue and white, that began the show.

Another example: a plaid sleeveless top in black and white with an unexpectedly sexy, skin-baring crisscross back.

"It's all about being playful, and breaking expectations," Lam said in a post-show interview. "My work has always been rooted in American sportswear. So I'm just loosening it up, relaxing a bit."

One could also see a loose, playful feeling in Lam's so-called "Pajama" tops and pants, roomy but still structured; in the matching turbans that accompanied a number of outfits, particularly the plaid ones; and in the hippie-esque "fringe belts" that were draped across skirts or dresses.

There were also cute, very short capelike tops in crepe, recalling the designer's fondness for longer capes in the winter.

Lam said he enjoyed playing a bit with colours, particularly the injection of yellow into his collection. "It's such an optimistic colour," he said.

And he noted he was playing with textures, too. Those plaid garments? They were actually made of a light cotton faille material.

"It's unexpected," Lam said. "Playfulness, that's the important thing."