One of the main questions we get asked is "why is my soap brown?"
It is often caused by vanilla, which is a flavour derived from orchids. Vanilla pods start out very green and then darken to brown as they age and ripen. The darkening is caused by various reactions in some of the components. One of those is vanillin, which is the organic compound that gives vanilla its flavour. Vanillin discoloration is a 100% natural process.
Depending on percentages used, the soap can discolor anywhere from off-white to dark brown. It usually takes a few days to appear, although certain scents may not discolor for a few weeks. It shows up first on the part of soap that’s exposed to air. That means the sides discolor, but once you cut into the bars the middle is still white. Eventually over time, the whole bar will darken.
We use vanilla in our Rose and Sandalwood soap/shampoo bars, so you will often see discolouration in those. It is perfectly normal. Other fragrances can also do the same, and we see the same process happen in our Lime Soap/Shampoo bars as well.