Custom Preview Issue (Same colour for all geometries)

Hello,

Today I opened an old rhinoceros 6 .gh definition in rhinoceros 7. The code still works but I have a problem with the custom preview. As you can see in the image, in the rendering mode i see only one colour despite I have connected different colours in the “custom preview” component. Even if I change the other colours in the custom preview component, I can’t manage to update the colour.
Any way to resolve this graphic issue?

Thanks in advance