Welcome to Daily Halacha. Can one spray cologne on Shabbat? The Chachamim (Sages) tell us that on Shabbat there is something called issur (prohibition) molid reiach. You now create a scent, a smell, on Shabbat. Therefore, when you spray cologne on fabric, clothing, or your shirt, you transfer the smell from the cologne onto the shirt or material. The smell then stays on the clothing or material, so it is as if you created a new smell on the shirt. You had one cologne with a good smell; now you have the cologne with the good smell and the fabric and shirt you sprayed it on. So we consider that creating a new smell. It is called molid reiach: You gave birth to a new smell, which is an issur on Shabbat.
However, if you spray directly on your skin, on your or, it's allowed on Shabbat. So are you allowed to spray perfume? The answer is: not on clothing or material, but you are allowed to spray it on skin. Why are you allowed to spray it on skin? Because the natural oils of our or, of our skin, and the sweat remove the smell of the cologne much faster, so we consider the cologne on your skin not really to be reborn. We don't call that molid reiach. On clothing, it stays longer, long enough to be considered creating the smell, molid reiach. On skin, it doesn't. Therefore, you are allowed to spray cologne on your skin, but not on clothing on Shabbat.