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