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