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