In the artist Alia Penner’s eyes, everything looks better covered in rainbows. Not girly, pastel rainbows, but brilliant acid hues that bring to mind Peter Max and Sonia Delaunay. When the California-born artist isn’t painting rainbow-framed portals into alternate universes, she brings her pop psychedelic sensibility to album covers and posters for L.A. bands and happenings, helping to define the contemporary look of the city. Now, after dipping her toes into fashion with illustrations for Erin Wasson’s RVCA ad campaign and the hand-lettered titles for a Missoni film by Kenneth Anger, Penner, the former fashion editor of Arthur magazine, has introduced Mombi, a line of dresses named for a witch in Frank L. Baum’s Oz series, at Colette in Paris.

Created with her friend Katie Casey, an L.A.-based designer and wardrobe stylist, Mombi came into being when the photographer David Mushegain asked Penner to participate in a pop-up shop accompanying his “Don’t Call It Cool” show of California youth culture at Colette. Unable to lug a stack of paintings to Paris, she needed something that could fit in a suitcase. Et voilà: Cosmic Love and Sail ’77, two whisper-light chiffon frocks digitally printed with Penner’s intricate, prismatic collages.

Available through August at Colette’s eshop, the sheer, oversize dresses — a little bit ’30s, a little bit ’90s — fit a wide range of body types. Casey encourages women put off by the size to simply try one on. “We’ve been referring to them as ‘magic dresses,’” she says, “because they look good on everyone.”