Despite the names of the palettes iron and iron_darker, the lightest three colors in both palettes are identical.

Steps to Reproduce:

• On a word with 1.20 experiments enabled, apply Coast iron trims to an iron and diamond chestplate
  • Coast contains the three lightest colors of the palette which is why I chose this one
• Place down two armor stands next to each other and place each chestplate on one armor stand
  • Notice the identical light colors

Locating the image files:

• Navigate to the version jar under .minecraft\versions\23w05a
  • If on a Windows system, you can type %appdata%\.minecraft\versions\23w05a in the Run window (Win + R) for quick navigation
• Open the jar file with an archive software such as WinRAR (or make a copy of the jar file somewhere and add .zip to the end of the file name past the file extension and open it)
• Navigate to assets\minecraft\textures\trims\color_palletes
• Locate the iron.png and iron_darker.png image files in the directory

Upscaled versions of the palette files are attached as well as a file with both palettes adjacent to each other to present the identical colors.

While the rest of the colors appear to be flipped between the palettes, that is being tracked in MC-259635.