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