blender vertex color to seams

vertex_color_to_seams.py

import bpy
import bmesh

# Assume triangulated mesh

object = bpy.context.object

bm = bmesh.from_edit_mesh(object.data)
bm.calc_loop_triangles()
bm.edges.ensure_lookup_table()
bm.faces.ensure_lookup_table()

color_layer = bm.loops.layers.color.active

def get_edge_color(edge):
    edge_color = None

    for loop in edge.link_loops:
        loop_color = loop[color_layer][:]

        if edge_color == None:
            edge_color = loop_color
            
        
        if loop_color != edge_color:
            return None
    
    return edge_color

def get_full_face_color(face, exclude_verts):
    face_color = None
    
    colors = []
    for loop in face.loops:
        loop_color = loop[color_layer][:]
        colors.append(loop_color)

        if loop.vert in exclude_verts:
            continue

        if face_color != None and loop_color != face_color:
            continue

        face_color = loop_color

    return face_color

for edge in bm.edges:
    edge.seam = False
    edge_color = get_edge_color(edge)

    if edge_color == None:
        continue

    face_colors = []
    for face in edge.link_faces:
        face_colors.append(
            get_full_face_color(face=face, exclude_verts=edge.verts)
        )
        
    # Exclude boundaries
    if len(face_colors) != 2:
        continue
    
    # Face are the same colors, no seam needed
    if face_colors[0] == face_colors[1]:
        continue

    if edge_color == face_colors[0]:
        opposing_color = face_colors[1]
    else:
        opposing_color = face_colors[0]
    
    if edge_color < opposing_color:
        edge.seam = True