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