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