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