A color material aqueous solution having excellent thermal stability under acidic conditions, a method for manufacturing such a color material aqueous solution, and a blue-colored beverage are provided. Provided are: an acidic color material aqueous solution containing phycocyanin (A), a polyvalent carboxylic acid (B) containing one or more hydroxy groups, and at least one kind of nonionic emulsifier (C) selected from the group consisting of sucrose esters and polyglycerol esters, the at least one kind of nonionic emulsifier (C) having an HLB of 15 or more; a method for manufacturing an acidic color material aqueous solution including a step of dissolution in water (D); a method for manufacturing a color material aqueous solution in which the raw materials are dissolved in water; and a blue-colored beverage.