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