—Administrative document images are usually processed in black and white what generates many problems due to the errors related to the binarization. Besides all semantic information provided by the color is lost. Document images have a rich and highly variable content. The presence of false colors and artefacts introduced by the scanning and the compression alter the segmentation of the regions. Problems arise when there is no correspondence between the point clouds which are detected in a color space and the real regions of an image. In order to help the segmentation, we propose the extraction of the main colors of an image as a set of binary layers. Due to the industrial context, our approach has to run unsupervised on a generic dataset of color administrative documents. The originality of this approach is the use of a multiresolution analysis to detect the number of colors automatically. At a low resolution, a set of local regions is obtained thanks to a SLIC-based approach which takes into account the structure of documents and which combines both colorimetric information and spatial information. Then, a merging stage is applied on each resolution separately based on the colors which have been extracted at a lower resolution. This contribution can both feed the traditional process and exploit colorimetric information.