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