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