I was playing earlier this morning and though I'd share a couple of images with you on the off chance you might find them amusing...
This is an image I took in Gough's Cave in the Cheddar Gorge. It is shot in 'natural' light and has not been coloured in any way.
If we saw colours at the infra-red end of the spectrum, the image would appear like the above.
And finally, this is the colour inverted (negative if you like) version of the same image.
Here's another pair of images... I entitled the original "Maiden's Prayer"... I dare say you can work out why! 
Hope you find these interesting...






