Disclaimer: I am not a lawyer. This is not legal advice. The information below is to be used solely for educational and entertainment purposes only. This comes from my understanding of copyright courses that I have completed as part of a software development degree. Copyright laws will vary depending on jurisdiction.
Copyright is the right given to creators to make copies of works in which the medium of expression is of critical importance. Things that do not qualify for copyright include: things that are basic or commonly known, ideas (as in concepts that have not been made concrete), or titles and names.
From this definition, colour is not copyrightable. Colour is an aspect of the electro-magnetic spectrum, which means it cannot be expressed in other mediums. Furthermore, colour would fall under the spectrum of basic information. Therefore, colours do not qualify for copyright protection.
That being said: It can be trademarked, and things that produce colour can fall under patents. Pantone, for instance, likely has a patent on their markers and the formulations used to produce the tinting from markers. I’ve taken a look at pantones website, and they appear to sell markers as well as colour samples. They would hold a copyright over the design of these prints, but not the colour advertised.
And as Kynlo above mentioned, colours may be trademarked. However, you wouldn’t be violating trademark for simply using these colours. You would likely be violating trademark if you were to use these trademarked colour to misrepresent your brand as the trademark holder. But there’s nothing stopping you from using the colour in your painting.