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