You need to use a different pen set in layout. We do all our modeling work and views in color (colour) but these pens are mapped to black and grayscale (greyscale) in layout.
If none of this makes sense to you, I would advise spending some time with the manual reading about pen sets.... HTH.
Nattering nabob of negativism
2023 MBP M2 Max 32GM. MaxOS-Current