Many of these conditions also cause the tongue to be red, which can stem from a vitamin deficiency, WebMD states. Someone who is lacking in vitamin B12 or folic acid is at risk of having a red tongue. Another cause for a red tongue is a geographic tongue, which is sometimes referred to as glossitis. This causes reddish spots on the tongue that look like a map. Some patches of red also have whitish areas with geographic tongue. If the tongue is also sore due to this condition, topical medications are available.
Sources: webmd.com, webmd.com