Do you mean "sweet" as in "floral" or as in "foodie?" Most foodie fragrances contain vanillin so you can just about always count on them discoloring. And bless BB for going the extra mile in reporting discoloring fragrances! Nature's Garden has a good Almond Marzipan that doesn't discolor, so you might test a small amount of that one. And don't discount brown soap right off the bat. I have several friends who request it as long as there's some kind of interest like an exfoliating ingredient - colloidal oatmeal, jojoba beads, various seeds, etc. Even a little glitter or unfragranced batter in a different color swirled into the top can look lovely. There's usually some way you can dress up a brown soap, so have fun experimenting!
What colorants have you tried so far? For bright eye-popping color, I usually go to the micas. Neons work great too but I've had issues with acceleration with some of them. It's entirely possible it's just my recipes though. You might try making a small, one-pound batch and test each of your colors in individual small molds just to get the hang of how much you need to use. Small plastic yogurt containers make great molds for these kinds of tests. I like pigments (ultramarines, oxides) for pastels, and can usually mix the colors I want with the basic chrome green, yellow oxide, burgundy oxide, and ultramarine blue. Saves a bit of money to mix my own instead of purchasing ready-made tints, and I have fun with it too.
