You can. Depending on the conversion, the results differ.
Often the colours that come out will look weird. People use "Channel swapping" to get more pleasing results.
At first glance it may appear like just another high contrast black and white, but things react differently to IR. Plants/foliage for instance, reflect almost all of it (otherwise they'd heat up), and thus appear white under IR. Bodies of water absorb it, so appear black. Skin becomes much more uniform in tone and veins become visible (It's really weird), and radiative heat sources glow.
On my 720nm camera, with default colours the sky shows a rusty red colour. By channel swapping red/blue I got the following -
Infrared Test by
Jamie Moulton, on Flickr