Despite methanol is toxic to human health and causes serious damage to automobile engine and components in fuel system, there are increasing distribution of methanol-containing gasoline in some area. Methanol demonstrates similar chemical properties to ethanol (which is established as an additive to gasoline), so that it is challenging to identify methanol-containing gasoline without performing proper chemical analysis (e.g., GC-MS). In this study, we aim to develop low-cost, portable, and easy-operation sensor that selectively changes its color (from red purple to blue purple) in response to methanol-containing gasoline. The colorimetric sensor will be useful for automobile users to avoid unexpected refueling of methanol-containing gasolines. Our methanol sensor is a thin film of clay mineral (layered double hydroxide, LDH) embedded with dye molecules (oxoporphyrinogen, OxP). For the purpose of improving magnitude of color change (sensitivity) and selectivity to methanol, we tried to select suitable clay structure and optimize anion species involved in clay minerals. At first, we tried to select suitable clay structure, for example Mg : Al ratio in LDH. However, it supposed to be the Mg : Al ratio in LDH did not influence sensor performance, and the next examination squeezed a target for the optimization of the anionic species(acidity, electric charge, polarity) in clay minerals. Consequently, the selection of the anionic type was effective and the optimized sensor clearly and quickly changed its color in response to methanol-containing gasolines, for example 12 wt% methanol. In contrast, color change was negligible for gasoline containing 10 wt% ethanol. Thus, our colorimetric sensor is promising for facile identification of methanol-containing gasoline.