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