The speaker describes their blood as full of love, but a strange kind: love that stays hidden and can't be found just by appreciating it. Because it's concealed, the speaker says it has "less hue but great saturation," borrowing language from color to suggest a feeling that looks faint on the surface but is intense underneath. The bright, citrusy "tangerine blood" is an unusual image, warm and almost cheerful, which makes the poem's last line land harder. After repeating that the blood is "full of hidden love," the speaker admits it is "but mostly hatred."
That final turn reshapes everything before it. The speaker seems to be guarding a tender feeling beneath a much larger bitterness, and may not trust anyone to see the love anyway. The mood is guarded and quietly bruised, with a flat, confessional tone. The title, "Fallen angel," hints at someone who once felt purer and now feels cut off from that goodness.