The first camera perspective shows the building from the 3rd floor looking eastwards:
The first image is rendered by Indigo and looks more blueish than the second one, rendered by Luxrender. Both images rendered in over 64 hours (the Luxrender one I allowed 70 hours). I have chosen the camera/tonemapper settings so that the staircase in the middle was slightly overexposed (mainly white), the sky is still visible as blue on the top, but the bright sun light casting the shadow of the staircase against the walls in the lower part still shows the stripes separating the windows on the top of the building.
Otherwise both images a prettly close to each other, they both show the caustics, created by reflections of the airplane wings, in the upper left corner of the image. The Indigo rendering seems to allow more bounce light (or a higher energy bouncing around), so the blueish color seems to be caused by the color bleeding of the blue floor material onto walls and the (grey) ceiling.
The second camera perspective turns the camera around and shows the building from the 3rd floor looking westwards:
This time we can see that the sun light is entering the building not only through the top windows, but also through the west glass front. The staircases are well lit, but not overexposed, the sky is too bright to show blue, but the reflections show the other (east) glass front and some blue sky from that direction. The darker color in the lower part of the (west) glass front is caused by a building obstructing the sun rays. We can see stripe patterns on the rounded walls which are caused by reflections of the railings.
The last camera perspective shows a staircase from below (looking eastwards):
The upper left corners are slightly overexposed, you can see how the color bleeding picks up far more blueish color in the Indigo rendering. The Luxrender version is missing stronger reflections in the railing material. This could be changed in future versions of the exporter.
Finally I want to talk about the blue vs. the black stripe in the lower part of both images. The CG pinhole camera is placed directly on the (blue) floor, which is impossible to do with a real camera, but in this case it leads to the visibility of the floor within the Indigo image, whereas the Luxrender camera seems to clip the floor from the viewing frustrum, which leads to a black color. Anyway, placing the camera slightly higher should solve the problem and the bouncing of the light happens correctly in both cases.