HD630 iGPU display color distortion problem (OpenCore, Big Sur)

Hi all, can't seem to get past this bug in my new install. I posted a few times in the discord but couldn't get any bites.

My display is consistently distorting colors, as you can see in the image of my dock (orange finder, etc.):

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distorted task bar

I followed the Dortania guide to install with OC v 0.6.4 and then followed the iGPU patching steps in the post-install guide to no avail.

I've come across multiple old posts on tonymacx86 (like this one: https://www.tonymacx86.com/threads/solved-color-inversion-on-every-screen-refresh.218983/) that fix the problem by installing SwitchResX and selecting "millions of colors". I've installed SwitchResX for Big Sur but I don't see such an option :(

I'm using the integrated graphics on my chip to drive the display, and connecting with HDMI. I've also tested with a different monitor. Any suggestions are much appreciated. My system specs are listed below:

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display specs

macOS Big Sur (11.1), installed with OpenCore v 0.6.4

SMBIOS: iMac18,3

CPU: i7-7700k (Kaby lake)

Mobo: MSI Z270 PC MATE

RAM: Corsair Vengeance 16GB (2x8

Storage: Samsung 970 Evo Plus 250 GB NVME

Monitor: LG 27GL850-B 27"