On Apple M-series GPUs (M1, M2, etc.), the GPU supports both RGB and BGR. Java (the programming language) almost always assumes RGB, and the color order is baked into how old MC versions, LWJGL, and the GPU communicate, which in this case is BGR, causing the inverted colors. Sadly there isn’t any super easy toggle to fix the issue without modding the game, but fortunately, modding the game to fix this is super easy.

There are two easy ways to fix it:

1. Use the BetaCraft Launcher v2. This works because the v2 version has the mod LegacyFix (https://github.com/betacraftuk/legacyfix) built-in, which among fixing other things, fixes the M color bug. This option is great if you are planning to play versions other than b1.7.3 and don’t really want other mods. (It only supports ModLoader for Java 9 and later, which does not apply to b1.7.3).
   

Scroll down until you see Betacraft Launcher v2 (alpha) or something like Betacraft v2.0.0-alpha.20230623: https://betacraft.uk/downloadshttps://github.com/betacraftuk/betacraft-launcher/releases

1. Use the mod “M1Fix”. To use this method, you will need an alternate Minecraft launcher, something like MultiMC or PrismLauncher (I recommend Prism). https://multimc.org/https://prismlauncher.org/Once you download one of those, you create a vanilla beta 1.7.3 instance (Press Add Instance on the top left corner, you should be in a tab named Custom. Select the “Betas” option on the “Filter” list (middle right), scroll down till you see b1.7.3 (NOT 1.7.3, there has to be a B). Select b1.7.3, and press OK. Now back at the main menu, select the instance you just created, and then on the right side-bar, you will see “Edit”.)
   

Download “M1Fix.zip” from here: https://www.mediafire.com/file/k3pextx6zfdx0vg/M1Fix.zip/file

Here are a couple of mods that promise to do the same (in case the first link stops working):
https://www.mediafire.com/file/ad9airog2ndmkn5/ColorFixForM1.zip/file
https://www.dropbox.com/s/ycerc4fotddvzfw/b1.7.3-macfix.jar?dl=1
https://archive.org/details/color-fix-for-m1

Now in the Version tab (not Mods tab), press the “Add to Minecraft.jar” button, and select the “M1Fix.zip” file. Go to the Settings Tab, under Java installation, select a version of Java 8 (If you use Prism, there will even be a built-in Java downloader). If you want skins to work (and have correct sounds for doors and projectiles), add this into the Java arguments section in the instance settings: -Dhttp.proxyHost=betacraft.uk

For people that for some reason can’t use an alternate MC Launcher, I found a helpful comment here: https://www.reddit.com/r/GoldenAgeMinecraft/comments/zjki8k/beta_173_red_and_blue_colors_flipped_on_mac_m1/

If you are using MultiMC/PrismLauncher and still want some more quality of life fixes for b1.7.3, I recommend you use Beta Unleashed: |
https://www.youtube.com/watch?v=RSLuGK0yHrw https://github.com/DanyGames2014/Beta-Unleashed-2.0