Before we get into how you can get better with seeing and using color let us discuss why talking about color is important:

Far gone are the days of black and white only. Almost everything we visually consume is in color. If it is not it is an artistic choice but we are no longer limited by technology to only display monochromatic to consumers and thus can communicate many more messages to these consumers.

This is highly important in the field of advertising as colors help to contribute to the appeal and make more sales. The appeal and emotion portrait in images are also important in the fine arts. So, we need to know, understand the theory behind it and we need to practically use this knowledge to create more value for our customers.

The 80/20 Rule of Retouching:
As an experienced retoucher, I know that the most time-consuming tasks only contribute about 20% to the effect of the final image and yet can take up to 80% of your time spent on an image.

In reverse this means, there are tasks which only take up little of your time and contribute hugely to improving an image.

Color is one of these retouching tasks!

With just a few, well-done adjustments you can drastically alter your image (hopefully for the better). I say this to put emphasis on how important it is to be good not only with skin clean up, dodging and burning, hair retouching, but with color theory and its application.
Promises Of The Internet
When you browse the internet for solutions you are getting sold everything around color. Tons of Quick Solutions, how to get results in no time, easy cinematic color grading, learn the art of color, mastering advanced color grading (a course for 15 bucks), color grading made easy, tons of actions for fine art, fashion, professional color grading styles,...

In short: you really have to look hard to find structured information that is not based just on how to manipulate color with a certain program or the typical "this is how I do things, hope it works for you too".
It Is A Process
None of these courses I found provide you with the information you need to make your own reasonable decisions. That is why I decided to make this episode and give you a few tips on what you can look up, try and practice with. And over time, your color vision and knowledge will increase.

Please, note that it takes time and practice. While you might think you cannot change the way you see color as of it being a purely physical factor, please, let me tell you wrong in this. My color vision once was quite bad too!

I remember, when I was getting into retouching. I browsed a lot of forums and also looked up competitions in there. I could not understand how they could favor some images over others.

I even remember one forum member mentioning that he or she could clearly see how far ahead in terms of technique and quality someone else was in that thread, while I was wondering "what the heck was different" in these two's images.

Over time this changed for me. It surely is different for every person as we all have different abilities to begin with but when you make improvements you all the sudden will see things you never noticed before!
Color vision can be trained!
Learn About Your Strengths And Weaknesses
A good way to determine how your color vision currently is is to use the X-Rite color test.

The test is really simple. You are to bring a few color swatches in order. In the test, they target specific hue ranges, and if you lack the ability to see or better differentiate within a certain hue range they will let you know after the test, including a visual representation.

Here are my current results. One try, no cheating. But remember,