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