I have some small light spots on my LCD that never go away.
On black, I don't see any spots.
On any other color—for example if it is a red background—I see faint red color on those spots location.
So is it a dead pixel or stuck pixel? FWIW, this happened just after cleaning the LCD with a cloth while it is turned on.
Here is a picture of my screen. The bright spot is on the right:
A "dead" pixel is one that is turned off and will not turn on. So it is always black.
Any pixel that is some color other than black and remains a consistent color other than the color it is supposed to be displaying is "stuck".
Other issues, such as inaccurate color or light levels in a pixel of group of pixels indicates some other problem with the panel.
None of these visible issues will be captured by a screenshot because the screenshot only captures an image of the information being sent to the screen by the computer, and all of these issues are with the screen itself and the computer has no way to know about them.
All of these issues indicate a problem with the panel, the physical screen itself. Some of them COULD be repaired using the tips mentioned in the question linked in the comments above, but many of them cannot be repaired.
It's very difficult to say exactly what the issue is without seeing the panel in person. However, I expect it would be one of the following issues - all of which are physical damage. I'd vote for #1.
The panel has been physically hit / damaged from the rear, causing the layers to become malformed. This effect can happen if the "Bottom Chassis" becomes dented and applies constant pressure to the rear of the panel.
The front surface (possibly even the polarizer itself) has been physically damaged or had a substance deposited on it. If your cleaning was particularly vigorous or the solution you used affected the panel, then it's entirely possible that the matt finish of the panel could have been reduced, or conversely could have collected additional material. Try "huffing" on the panel and wiping it away with a microfiber cloth.
The panel has got moisture inside it, most likely between the reflector, light guide, diffuser and prism sheets, but also potentially at the front. As the layers of the panel are so close together, it's possible for moisture to get quite a long way into the panel by capillary action. Did you use a liquid cleaner, and did any drops make their way to the edges of the panel?
This diagram from Samsung shows the layers in a modern LCD:
From the photo you've shared it definitely isn't a dead or stuck pixel or any other LCD defect, as this would typically be only one pixel (or sub-pixel, or row / column) in size, and would have sharp edges with dramatic color changes.
