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