If you are new to soap making you may not yet engaged in vanillin warfare, but rest assured you will. I call it the Browning Battle and one rarely wins. Here is a recent test we did using our Non-Darkening Vanilla fragrance oil in both cold process (right) and melt and pour soap (left). This particular fragrance is not intended for use in CP (cold process) soap, but I wanted you to see the results. Believe it or not, the soap on the right was white when we started out. As you can see, over the course of a few days it darkened to a deep chocolate brown.
The white melt and pour soap was less dramatic, but you can note how it has change to a rose color. The Non-Darkening Vanilla fragrance did help, but it did not keep the soap white. It didn't darken to a brown shade, but it also did not work as well as we had hoped. My next test will be to see how this fragrance performs when the soap is colored. Since we now know that the soap will lean toward a rose color, we can factor this into how our color choice will ultimately display.
Based on the color wheel, we know that the rose color is a red hue, so adding blue to the soap is likely to produce more of a lavender shade. Vanilla is such a wonderful scent and also found in many other fragrance types such as Peppermint. You don't want to avoid these great fragrances, you just need to learn to work around them by testing in small batches and make notes of your successes for future batches.