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