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