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