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