Red Wheat Malt is malted from red wheat varieties rather than the white (soft) wheat most common wheat malt on homebrew shelves comes from — the same basic distinction that separates red and white wheat flour in baking. The flavour follows: Red Wheat Malt reads somewhat nuttier and more robust than standard or white wheat malt, a slightly more assertive wheat character rather than the gentler, more delicate profile white wheat malt is chosen for.
At 2.5-4 °Lovibond and roughly 90 °Lintner diastatic power, it converts and behaves functionally much like any other wheat malt — self-converting with a comfortable enzyme margin, and subject to the same husk-free lautering considerations that apply to wheat malt generally, meaning a high percentage still benefits from rice hulls to avoid a stuck sparge. American wheat ale is the style most likely to specifically call for Red Wheat Malt, since American wheat beer traditions lean toward a more robust wheat character than the delicate profile German Hefeweizen or Belgian Witbier are built around. It's less universally stocked than standard wheat malt, so sourcing it usually means checking with a specialty supplier rather than assuming any homebrew shop carries it. Where only standard wheat malt is available, substituting it at the same weight is a reasonable approximation, with the understanding that the finished beer will read a shade more delicate than a Red Wheat Malt-based recipe intended.