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