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