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The yellow shades will not increase CRI. It just blocks out the blue wavelengths. Actually I found that blue wavelengths get blocked the easiest. Using any diffuser will lower proportion of blue wavelength a good amount.

For me, I have the whites on my monitor calibrated to 3000K with DUV = 0.000 using Windows night light settings and my monitor’s color settings. I measured a very significant drop in blue wavelength output setting it to 3000K. When night light settings first come on, the screen looks unbearably yellow and it takes about 10-20 minutes for my eyes to adapt and no longer find it yellow. What I find helps my eyes adapt faster is by using bias lighting behind the monitor. If you use a bias lighting warmer than your monitor’s cct, your monitor will not look yellowish. For example, if you use a 2000K bias lighting, a 3000K monitor setting will look almost cool white. Bias lighting on its own also benefits your eyes because it increases lighting in your peripheral vision, which causes your pupil to constrict so less blue light enters your pupils. This is the reason why people say it’s bad for your eyes to play on the phone in a dark room.

I find the best bias lighting to use is the Auxma 5050 2400K 95CRI after testing many different LED strips due to its close to the BBL tint (too far from the BBL will cause your monitor to look pinkish or greenish) and one of the lowest blue light output I’ve seen in this color temp. You can buy a cheap usb bias lighting from Aliexpress and cut out the led strip and connect the Auxma strip to it.

This is what I tested for the Auxma led strip

Auxma 5050 2400K DC12V CRI 95
CCT: 2329K
DUV: –0.0015
CRI (Ra): 95.7
R9: 94.5
Rf: 95
Rg: 103
Blue Peak: 18% of max

If you want to use a flashlight for bias lighting or as a bedside light, nothing beats the E21A 2000K, which has a neutral DUV of 0.0000 and the lowest blue light output I’ve ever seen in any LED or any lighting for that matter. It produces even less blue light than incadescent and halogen bulbs.