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