A 4mm wide strip will not fit into its own metal holder. The most advantageous solution is to use 3 mm wide strips. Color distortion is not a big problem. The colors are initially of low quality due to outdated technology and poor choice of oscilloscope interface colors by the developers of the device themselves.
After replacing with LEDs, you will get a color correction effect similar to the images below (It is necessary to adjust the current on the LEDs to a safe value). But the screen itself will not allow you to make the image perfect. Viewing angles will remain just as bad.
Personally, I like the picture after correction better.
I used a cheap "Universal LED Backlight Strip Light Kit. CCFL Screen To LED" from China from Aliexpress.