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