What method SnapTo a layer name or colour of that layer

Hi,
V5
How can I have my snaps snap to a curve, the snap being decided by a layer name or colour in use for that layer ?

and just where my mouse cursor is in the build area, not have it snapping to anything for that colour all at once !

I have a lot of near together lines and wish to ignore them except a particular line whilst using them all visually for what I am doing.

Cheers

Steve