1. A method of displaying a plurality of color images simultaneously, including a color map administration process and a plurality of display processes each for displaying respective color images, simultaneously, said color map administration process comprising the steps of: receiving a write request with color map data and an area identifier issued from one of said plurality of display processes for writing color map data in one of a plurality of memory areas, securing a memory area from the plurality of memory areas and writing the color map data in the secured memory area; setting a pointer to the secured memory area associated with the area identifier in an administration table; and obtaining an offset corresponding to the color map data in the secured memory area from the administration table and transmitting the offset to the one of said display processes issuing the write request, and each one of said display processes comprising the steps of: issuing a write request with color map data and an area identifier to said color map administration process for writing the color map data in one of a plurality of memory areas; receiving an offset corresponding to the color map data written in the secured memory area from said color map administration process; and displaying a color image by using the color map data in the secured memory area on the basis of the received offset.