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)(11,20)(12,17)(13,16)(14,18)(15,19)(21,24)(22,23)(25,26,30,32)(27,31,35,38)(28,33,36,39)(29,34,37,40)(1,3,5,8)(2,6,4,7)(9,11,15,13)(10,16,19,20)(12,21,18,23)(14,24,17,22)(25,27,30,35)(26,31,32,38)(28,29,36,37)(33,34,39,40)(11,13)(16,20)(21,23)(22,24)(26,32)(27,35)(28,36)(34,40) involution — undirected(1,2,5,4)(3,6,8,7)(9,12,15,18)(10,17,19,14)(11,21,13,23)(16,22,20,24)(25,28)(26,33)(27,29)(30,36)(31,34)(32,39)(35,37)(38,40)(9,13,15,11)(10,16,19,20)(12,23,18,21)(14,24,17,22)(25,26)(27,31)(28,33)(29,34)(30,32)(35,38)(36,39)(37,40)(1,4,5,2)(3,7,8,6)(9,14,15,17)(10,18,19,12)(11,22,13,24)(16,21,20,23)(25,29)(26,34)(27,28)(30,37)(31,33)(32,40)(35,36)(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.