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