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