The color images use HSB color space. The color represents distances from closer to further away in reverse ROYGBIV order (VIBGYOR actually). The color images use HSB color space. See the HSB Wikipedia page for a visual explanation. The grey-scale images represent distance by showing closer objects darker and further as lighter.
The color images are better for showing lots of small changes in deapth while the grey-scale are better for showing consistent gradients and large changes in depth. Picture 6 shows the raw image with noise caused be the servo with out digital smoothing written into the arduino code.