There are a few different keyboards out there using Kailh Blue with RGB lighting...Rosewill RGB80 and its cousins (Xenics/iOne Scorpius M10TFL, Qpad MK-10), Tesoro Lobera Supreme (also available dual-branded as "Xenics Tesoro Lobera Supreme"), and V-Ox G11. The V-Ox is pretty close to having a rectangular shape, but it does have some gamer-style details, and while it advertises 25 different lighting modes, I'm not sure what degree of customization is possible. The RGB80 and relatives, as well as the Tesoro, all suffer from severe limitations as to lighting modes; the last time I checked, they were all limited to 1 color at a time, with a restricted number of color choices, pending future software updates which may or may not ever occur.
One thing that's kind of a longshot is that you could try and hunt down a GS104. I don't know if they ever actually made any with the blue switch, or how many of them, if any, made it to the West before production was discontinued (it couldn't have been more than a handful), but it's rectangular, colorful, and seems quite bright going by pictures.
