Why is anti-sera AB pink in colour?

Anti-sera AB appears pink in color due to the presence of specific antibodies that interact with antigens in a test medium, often involving a dye or chromogen that produces a visible color change. This pink color can also result from the aggregation of immune complexes formed during the reaction between antibodies and their corresponding antigens. The intensity of the pink hue may vary based on the concentration of antibodies and antigens present.