Retroview runs through the vanilla graphics engine. That means it sits in the same Resource Packs list as any texture pack you use. How you order the packs decides what you see.
How pack order works
In the Selected column, packs higher in the list override packs below them. If two packs change the same thing, the top one wins. A normal texture pack changes block and item images. Retroview changes how lighting and colors are rendered. In many cases both can apply at once.
Setting up the stack
1. Open Options > Resource Packs.
2. Move both Retroview and your texture pack into the Selected column.
3. Hover over a pack and use the up and down arrows to reorder. Start with Retroview at the top, so another pack can't override its lighting and color changes.
4. Click Done and load a world.
5. Check that your custom textures are visible and that the retro lighting and color shift are still there.
If one effect disappears
- Retro look is missing: Another selected pack may also change rendering. Move Retroview above it, or remove that pack for a test.
- Textures look wrong: Disable packs one at a time to find which one is overriding the other.
- Low-resolution or simple texture packs usually suit the vintage-screen colors and older-looking blocks that Retroview adds.