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