changing color-paths via css in .png, virtuemart

Wall decals are designs that are cut out of sheets. These are available in different colors and made ​​right after order. The customer will be offered about 20 - 30 different foil colors. The selection is actually made with color buttons in Virtuemart. This is a module of [login to view URL] For the webshop there are several (2-3) product images per item. The motif is presented on a corresponding background, usually a living room with a corresponding wall surface. The images show different color examples (subject to lighter or darker wall color). To simplify the customer the right color choice the following should be implemented: As can be seen using the following link, a product image is saved as png. By appropriate choice of the color the #hex-code is loaded in a specified color-channel of the png. This functionality has to be mapped in Virtuemart. Within the admin then one color per color-set has to be selected as the default color for the right color-path. This is currently not possible. Moreover, the default color setup shall relate to all different images per product. In the frontend the color-change shall be directly due to the color selection. The selected color values ​​must be within the scope of the shopping-cart. This is already the case in the module "custom-fields-for-all" of breakdesigns.net. Here is the link: [login to view URL]