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