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