The current batch of pancams is being acquired with every filter under the sun. This gives us the options to play with colour to our hearts content. For historical reasons, I use a program called ER Mapper which imports multi-layer image files and can process the layers in various ways including RGB displays. You might want to try playing with other programs to see what can be done.

here are the results of some of that exercise. Note that I do not have access to the exposure settings of the camera, so if one band is exposed differently to another, I don't have that info. Nonetheless, the overall success of the exercise and the lack of obvious errors in sky colour suggest that the exposures are "balanced".

1) RGB from L4, L5, L6

Quite a "natural" looking balance of colours, with the rocks coming out a pale salmon-grey. Note that in several places, this salmon-grey tint shows through the dunes, suggesting that bedrock is buried immediately below the surface just about everywhere. Note the dark pebbles up above the rock outcrop, we'll see them again later in a different light. For now, they seem to be grey or bluish.

2) RGB from L2, L5, L6

This substitutes the near IR L2 filter for the true red L4 filter. The sky and dust are about the same, but the rocks come out a brighter pink, showing that they reflect better in the near IR than in the true red. Thus we get an overall reddening of the scene. The colours look wrong - like shots at sunset. I don't "like" the colours, but the information about IR reflectivity is part of learning what the rocks are made of. I don't know the answer, but it's an interesting data point. The scattered pebbles don't change much, so they don't have a peak in the IR.

3) Synthetic RGB from L4 & L6 only.

MOC images of Mars often use a red + blue 2-band dataset and synthesise a green = (R+B)/2. If we do this, we lose some of the depth and richness of the colours. The rocks become more yellow-tan and less salmon (we're basically bleeding some of the pinkness into a synthetic and erroneous green)

4) Right eye - UV "colours"

Here we have to go over to false colours, since none of these correspond to visible light, except for R1, which is "no filter" and captures the whole range from IR to UV. Unfortunately, they didn't shoot L1, so I can't compare the human visible range to the pancam visible. The colours here don't mean anything, they are just useful ways for the human eye and brain to input waveband data.

Examining the 7 available Right-lens bands, I find that the 6 UV bands are closely similar to each other. substituting one for another yields little variation, but there is a weak trend from R2 to R7. What I have done, to encapsulate the range of behaviour is to generate 3 synthetic colours. "Red" = R1 the total integrated spectrum from UV to IR. "Green" = the average of all UV channels (R2 to R7). "Blue" = R7, the most extreme UV band.

Note that the rocks end up a cyan colour. This is caused by low red values compared to the other bands - so we learn that these pale rocks are also more reflective in the UV thhan they are in visible light - another data point towards rocks classification, but I'm still no wiser!

OTOH, if you look at the small scattered rocks above the outcrop, they have a distinct red tone, showing that they reflect better in the visible than in the UV. They are different from the bedrock, and appear to be the same stuff as the small granules scattered everywhere. These are either remnants of a different layer that we don't see in local outcrop, or a "lag deposit" of surviving inclusions from the pale rocks. If the rare dots scattered across the pale rocks are inclusions, we would favour the latter. If they are just loose surface material, perhaps the former.

One can go much further, producing wierd technicolour images that are more art than science. There are gradients in the UV/Vis balance of the sky, and some suggestions that the loose pebbles are shiny and reflecting sky colour. Are these pebbles of shiny grey haematite? But there are only two materials here, however I play with the wavebands - the pale rock, and the dark granules.