The colour of a perfume I have not used in a long time has changed. Is it safe to use?

Fragrances such as perfume and cologne are extremely delicate products, as the fragrance components are dissolved in alcohol. The amount of alcohol decreases with every use, so usually the product colour will get deeper, and the fragrance will also get richer as it ages.
If you are not bothered by the change in the fragrance, then you should use the product.
If you want to enjoy the original fragrance as long as possible, replace the cap firmly after use, and store the bottle at room temperature away from direct sunlight in a location with a constant temperature. We recommend you aim to use a perfume within 1 year of opening it.