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