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)(11,15,12,14)(17,18,21,19)(20,23,24,22)(25,26)(27,33)(28,34)(29,32)(30,31)(35,38)(36,40)(37,39)(1,3)(2,7)(4,5)(6,8)(9,11,13,12)(10,14,16,15)(26,31)(27,34)(29,37)(36,38)(2,4)(3,8)(9,10)(11,14)(12,15)(13,16)(17,19,21,18)(20,23,24,22)(25,27)(26,28)(29,35)(30,34)(31,33)(32,36)(37,40)(38,39)(1,4,6,2)(3,5,8,7)(9,12,13,11)(10,15,16,14)(17,20)(18,22)(19,23)(21,24)(25,28)(26,27)(29,38)(30,33)(31,34)(32,40)(35,39)(36,37)(1,5)(2,3)(4,8)(6,7)(9,10)(11,15)(12,14)(13,16)(25,29,30,37)(26,32,31,39)(27,35,34,40)(28,36,33,38)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.