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