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