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