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