Yes. Just about an hour ago I captured a rainbow on an infra-red camera. This was taken with my EOS 1100D with the low-pass & IR filter removed and replaced with a filter to only let IR light through. Lens: EF 17-40 f/4L USM – And here is the result!
Yes. Not very impressive is it. But it was worth a try!
Here’s the same rainbow in normal light. Taken with my EOS 5D Mark III and EF 24-105mm f/4L IS USM
BONUS PHOTO: Just after taking the rainbow picture, a parrot landed in the tree opposite our window.