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