Red-β-D-GlcU (5-Bromo-6-chloro-3-indolyl-β-D-glucuronide,cyclohexylammmonium salt), also known as Magenta-β-D-GlcA; is similar to X-GlcU, but the product of the substrate is a red (λmax 565 nm) precipitate, which is easier to detect against the background of plant cells.