Zechariah 6:2 Kabbalah

בַּמֶּרְכָּבָ֥ה הָרִֽאשֹׁנָ֖ה סוּסִ֣ים אֲדֻמִּ֑ים וּבַמֶּרְכָּבָ֥ה הַשֵּׁנִ֖ית סוּסִ֥ים שְׁחֹרִֽים׃

In the first chariot were red horses; and in the second chariot black horses;

Read kabbalistic (mystical) interpretation of Zechariah 6:2: and classical mystical sources.