Excuse the terrible quality, but according to the Spanish branch of European retailer GAME, two new DS colors are due out in Europe this coming June - Lime Green and Deep Red. A third color dubbed Ice Blue is listed on the site as well, but that color has already been released in Japan, so it's not entirely new. All color variations are pegged for a June 13 on the site.
As per usual, Nintendo has yet to officially announce any of the new colors. Either way, GAME has quite the track record on breaking information regarding new hardware bundles and the like, so we would be hard pressed not to believe them.
Nintendo DS Lite [GAME]