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