How about a darker palm sugar (jaggery) instead of simple cane. I like to throw in a pound into some of my brews. It's pretty cheap at the local Indian market. Morticaixavier's recommendation of aromatic is good, too. It's provided a nice golden hue to some of my saisons.
If your saison is too dark for the style guidelines, then the style guidelines are wrong.It wouldn't be the first time.
How much cane sugar is in your recipe? I would just substitute some dark Belgian candy sugar for all or a portion of it. The final flavor difference should be minimal compared to adding something like chocolate malt.