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