Holiness is white as is the Dove of the LORD. The Dove represents the Holy Spirit. The Saints and the Angels are usually seen dressed in white as are the inhabitants of Heaven. White stands for light and life and creative power. White is worn by the King of Kings. His army rides on white horses. The Bride of Christ is is adorned with robes of white.
The use of white lends itself to representing righteousness (Daniel 7:9, Matthew 17:2, Mark 9:3, Luke 9:29, Revelation 1:12 - 14, 6:11, 19:8, 20:11) or pretending to be so (Revelation 6:2), or made pure (Daniel 11:35, 12:10, Psalm 51:7, Isaiah 1:18, Revelation 3:18, 7:9, 13 - 14). It also symbolizes wisdom (Revelation 1:14), holiness or dedication to God (2 Chronicles 5:12, Mark 16:5, John 20:12, Acts 1:10, Revelation 4:4, 19:14) or joy (Ecclesiastes 9:8).