Rory, In the other thread you asked, "but are there any RULES, GUIDELINES, That one can follow "

The short answer is there are no rules and many guidelines. You have good eyes as evidenced by your critique in the other post; I declined to comment on others' work but agree with your impression.

Rather than try to provide a training manual (there are lots of good guides out there), I can suggest some basic skills that will serve as tools as you dive into this huge area, which is really a technical art form, from my pov. Remember, this takes years to master at the application level once you understand the mechanics.

1) Learn to identify the differences in actual images between R-G-B, C-M-Y and their primary-complementary combinations. Learn to identify color imbalance in neutral and /or memory colors in highlights, midtones, and shadows. You'll get good results right away with neutrals; however memory colors like flesh tones are something quite different. For instance a caucasian face that appears too yellow can actually be too yellow, green, or cyan, or a combination of Y-G, or C-G, and you will often need to use outside clues to determine which it is. If you have three color sliders, knowing at a glance which one to leave at "zero" is a valuable and time-saving skill. That is only the first step -- the second is "how much?"

2) Learn to see how much tonal range is in your image and how much you want to include in your result. While a flat low-range image will obviously need to be increased in contrast; with a full-range image, you will often be faced with a choice of how much detail in the highlights or shadows you wish to preserve, and make sacrifices in other areas accordingly (as you alluded to in your other post).

3) Finally, and I mean last, learn something about curves and gamma. This is the most mathematically complex area, and perhaps the hardest to master. It basically "squishes" one part of the tonal range while expanding another. It affects perceived brightness, contrast, color balance, and detail, so it's not a tool for beginners. Gamma numbers are a logarithmic representation of the nonlinear relationships. Shoot some grayscales. Play with only the overall gamma first, not individual colors, and see what small adjustments do to the low, mid, and high areas in terms of tonal compression. Then try some actual images and see where you want more tonal differentiation and apply accordingly.

4) Be patient. Make a correction, save it, and look at it 20 minutes later next to the original and go with your first impression, always! Marathon sessions are not allowed here, because your eyes adapt and fatigue. What looked right at 3 am is going to look too red the next day. Don't work in the dark. Keep diffuse natural light in the room and take your eyes off the monitor frequently. Don't use alcohol or smoke (anything).

5) Practice, practice, practice. The way to get good (and fast) at it is do it a lot and make plenty of mistakes. Keep a conservative approach. Keep a log of your sessions and their results. You'll learn more from your bad results than the good. I hand-inspected well over a million photographic prints per year back in the day, and found that radical corrections don't sell, but almost any improvement over an imbalanced original is readily accepted. As the old saying goes, "You can't make a silk purse out of a sow's ear."

6) Run your results past others. If the video that you labored over for days looks too red to someone viewing it for the first time, it is probably too red. IOW, we learn to use technical tools to achieve subjective results. Obviously, much of what I have said comes from my work in conventional photography -- white balance, which is really a secondary anchor point, wasn't even a factor then . . .

Edit: Here is a collection of stepwedges, test patterns, and resolution charts I compiled several years ago, maybe someone will find them useful:
[Make new post if you want a copy of these]

Edit 2: Corrected some typos . .