It's my understanding that many herps cannot see into the infrared spectrum - though a number of diurnal species of reptile (bearded dragons and iguanas for example) do seem to be affected by the bulbs and these should not be used as a nighttime heat source for this reason.

Most red bulbs you see are simply painted red (not truly infrared), and therefore can be seen. I don't believe it is so much that they cannot see the red light, but it is much easier on the eyes than white light. Red light has a very low frequency and high wavelength; imagine sitting in a room lit by a standard 60watt incandescent bulb...now picture yourself in the same room with a 60 watt red bulb. The light is much less intense on the eyes, and you could probably sleep in this room with the red light.

You can find low wattage infrared bulbs at some pet stores, online reptile supply sources, and hardware stores, and even cheaper bulbs that are painted red. Regardless, I would only use the bulb for viewing during feeds and would not leave it on all night so that it does not disturb the frog. When using these bulbs with my Rhacodactylus geckos, I noted pupil constriction when they were exposed to the brightest area of light emitted by the bulb.