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