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