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