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