C. F. Keil and Franz Delitzsch on Exodus 25:4

Exo 25:4 תּכלת, ὑάκινθος, purple of a dark blue shade, approaching black rather than bright blue. ארגּמן, πορφύρα (Chald. ארגּון, 2 Chron, Exo 2:6; Dan 5:7, Dan 5:16; - Sanskrit, râgaman or râgavan, colore rubro praeditus), true purple of a dark red colour. שׁני תּולעת, literally the crimson prepared from the dead bodies and nests of the glow-worm,Glanzwurm: “the Linnean name is coccus ilicis. It frequents the boughs of a species of ilex; on these it lays its eggs in groups, which become covered with a kind of down.” Smith's Dictionary, Art.  Colours. - Tr. then the scarlet-red purple, or crimson. שׁשׁ, βύσσος, from שׁוּשׁ to be white, a fine white cotton fabric, not linen, muslin, or net. עזים goats, here goats’ hair (τρίχες αἰγείαι, lxx).