Why not pair a white polo with olive chinos? Both pieces are very practical and will look amazing matched together. Does this ensemble feel too polished? Let a pair of athletic shoes jazz things up. This look is probably exactly what you're looking for as an over-40 gent.
A white polo and olive chinos are both versatile menswear essentials that will integrate well within your casual routine. To give your overall getup a more casual finish, add a pair of athletic shoes to the equation. This outfit shows that in your forties you still have a vast array of sartorial options.