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