Different colours only come if ones 3rd eye is empowered, and meditated on a lot. Ofc everybody will have different experiences, one may see colours after the opening(very rare), one may see colours only after a year.
Also, if you doing the soul opening, you only have to open your chakras, and not empower them, and after every one of them are open, you can empower them, and then you might see colours with your 3rd eye.
So the answer is, if you feel the pressure when you meditate on your 3rd eye, it is open, and it goes with each chakras.