One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,8)(4,6)(5,7)(9,10,13,16)(11,14,17,20)(12,15,19,22)(18,21,23,24)(25,26)(27,36)(28,39)(29,34)(30,35)(31,37)(32,33)(38,40)(1,3,5,4)(2,6,7,8)(9,11)(10,14)(12,18)(13,17)(15,21)(16,20)(19,23)(22,24)(25,27)(26,32)(28,37)(29,39)(30,33)(31,38)(34,40)(35,36)(11,17)(14,20)(18,23)(21,24)(25,28,31,32,30,40,29,36)(26,33,34,39,35,27,37,38)(1,4,5,3)(2,6,7,8)(9,12)(10,15)(11,18)(13,19)(14,21)(16,22)(17,23)(20,24)(25,29,30,31)(26,34,35,37)(27,38,33,39)(28,36,40,32)(12,19)(15,22)(18,23)(21,24)(25,29,30,31)(26,34,35,37)(27,39,33,38)(28,32,40,36)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.