One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,6)(3,5,7,8)(10,13)(11,15)(18,22)(20,24)(25,26)(27,34)(28,31)(29,37)(30,33)(32,38)(35,39)(36,40)(11,15)(14,16)(18,22)(19,23)(25,27,30,28)(26,31,33,34)(29,36,38,35)(32,40,37,39)(9,10)(11,14)(12,13)(15,16)(17,18,21,22)(19,20,23,24)(25,26)(27,31)(28,34)(29,32)(30,33)(35,39)(36,40)(37,38)(1,2)(3,5)(4,6)(7,8)(9,11)(10,14)(12,15)(13,16)(17,19,21,23)(18,20,22,24)(25,28,30,27)(26,31,33,34)(29,35,38,36)(32,40,37,39)(1,3,4,7)(2,5,6,8)(9,10)(11,14)(12,13)(15,16)(17,20)(18,23)(19,22)(21,24)(25,29,30,38)(26,32,33,37)(27,35,28,36)(31,39,34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.