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)(11,20)(12,26)(13,14)(15,19)(16,24)(17,29)(18,28)(21,37)(22,25)(23,33)(27,36)(30,31)(32,39)(34,40)(35,38) involution — undirected(2,6)(7,8)(9,11,15,24)(10,16,19,20)(12,27,30,39)(13,22,18,33)(14,23,28,25)(17,34,35,37)(21,38,40,29)(26,32,31,36)(1,3,5,4)(2,7,6,8)(9,12,28,38,15,30,14,29)(10,17,13,31,19,35,18,26)(11,21,23,39,24,40,25,27)(16,32,33,37,20,36,22,34)(1,4,5,3)(2,8,6,7)(9,13,28,19,15,18,14,10)(11,22,23,16,24,33,25,20)(12,26,38,17,30,31,29,35)(21,37,39,36,40,34,27,32)(2,6)(7,8)(9,14,15,28)(10,18,19,13)(11,23,24,25)(12,29,30,38)(16,33,20,22)(17,26,35,31)(21,39,40,27)(32,37,36,34)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.