Color given objects on a pathway map with specified colors and return the URL of the colored image. In the KEGG pathway maps, a gene or enzyme is represented by a rectangle and a compound is shown as a small circle. Example of input: pathway_id: path:eco00260 object_list: (to add as list) eco:b0514 eco:b2913 fg_color: (to add as list) blue orange bg_color: (to add as list) red orange