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