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