Concise Bible Dictionary:
Purple Silk
A color often mentioned with blue and scarlet in connection with the tabernacle (Ex. 25:4, etc.). Among the spoils taken from the Midianites under Gideon was “purple raiment that was on the kings,” and it is used as a symbol of royalty (Judg. 8:26). In derision the soldiers put a crown of thorns and a “purple” robe on the Lord, as king of the Jews (Mark 15:17,20; John 19:2,5). The rich man in Luke 16:19 was clothed in purple; and papal Rome is seen as a woman clothed in purple and scarlet, royalty and splendor (Rev. 17:4; Rev. 18:12,16).