וְעָשׂ֖וּ אֶת־הָאֵפֹ֑ד זָ֠הָב תְּכֵ֨לֶת וְאַרְגָּמָ֜ן תּוֹלַ֧עַת שָׁנִ֛י וְשֵׁ֥שׁ מָשְׁזָ֖ר מַעֲשֵׂ֥ה חֹשֵֽׁב׃
And they shall make the ephod of gold, of blue, and purple, scarlet, and fine twined linen, the work of the skilful workman.
Read kabbalistic (mystical) interpretation of Exodus 28:6: and classical mystical sources.