Colloidal nanocrystals are appealing candidates for low cost optoelectronic applications because they can combine the advantages of both organic materials, such as their easy processing, and the excellent performance of inorganic systems. Here, we report the use of two-dimensional colloidal nanoplatelets for photodetection. We show that the nanoplatelets photoresponse can be enhanced by two to three orders of magnitude when they are incorporated in an all solid electrolyte-gated phototransistor. We extend this technique to build the first colloidal quantum dot-based bicolor detector with a response switchable between the visible and near-IR.