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