How to change WORKING colorspace in Lightroom

ngocv6163638 wrote:

However, when i change computer (also a 4k screen), the working colorspace change

No, that is not what happens since the Lightroom Classic color space cannot be changed. When you change computers, the difference is probably that the display profile being used on each computer is different. Color should be consistent if each profile accurately represents the capabilities of each display. But if a display profile is inaccurate or incorrectly applied (in Windows, not in Lightroom Classic), colors will not appear correct.

1. In Windows on your Razer Blade, make sure the active display profile accurately represents the Razer Blade display and is not something generic.
2. If that still doesn’t correct the problem, it may be necessary to create a custom profile for the display, ideally using a display profiling/calibrating device.

Lightroom Classic is used with thousands of displays that use several different color spaces in Windows and macOS, including sRGB, Adobe RGB, and P3. Yet without changing the Lightroom Classic working space, colors do display as consistently as possible across all those display color spaces — as long as an accurate display profile is set correctly on each computer.

Also, it doesn’t matter that both are 4K screens. The resolution of a display does not affect its reproduction of color.

A Working Space is an editing color space. As outlined, LR uses a very wide gamut Working Space based on but not ProPhoto RGB. You cannot alter this and don't have to. 

You can export to any RGB color space you desire. Outside applications that are NOT color managed, the concept of sRGB or any other color space is no understood; they are not color managed. So if you export to sRGB or any color space, you ideally need color management to view the RGB numbers correctly (matching on YOUR display what you saw in Lightroom). 

Also note, the only fully accurate way to view images in Lightroom is in the Develop module, ideally at 1:1. Outside of that module, the preview architecture differs slightly. 

IF you import an image into Lightroom that doesn't have a color profile, it assumes sRGB. Even if it isn't sRGB and that might result in a preview in Develop that looks odd. Otherwise, if the image is tagged and looks over saturated, IT IS. 

That, IIRC, is the signs of a corrupted monitor profile.

Look here on how to change it to sRGB for Testing purposes to see if your original monitor profile is corrupted.

How do I change my monitor profile to check whether it’s corrupted? - The Lightroom Queen

If one computer is showing different colors, you need to calibrate (both) monitors.

The "Working Color Space" used in LR is unique, built-in and unchangeable. It is called Linear ProPhoto RGB, which means it is defined by the same RGB primaries as the ICC recognized ProPhoto RGB space, but has a linear Tonal Response Curve. Because of the linear TRC, an image viewed in this space would be visually unattractive - dark and flat - so for viewing and histogram purposes the image is translated to a space called Melissa RGB, which is ProPhoto primaries and a TRC like sRGB. From Melissa RGB the image is then translated by the Color Management to your device's display space as defined by the OS's default display profile.

So, if the color is changing from one device to another, it is most likely because of improper color management caused by an improper, inadequate, or corrupt display profile.