Blender's new Mix node will not work on older version for blender 

if use saved the downloaded blend file with blender version 3.4 or later and reopened the blend file in older version the mix node will be marked as undefined

 there are 3 solutions

1. Redownload the blend file

2. update blender

3. Replace the undefined nodes with MixRGB node

Make sure the MixRGB nodes are looking good

If MixRGB nodes are masked undefined there are 3 solutions

1. Redownload the blend file

2. update blender

3. Replace the undefined nodes with MixRGB node

Shader work on both EEVEE and Cycles