Compositions, methods, and kits for stable Trypan Blue solutions are provided. In one example, a method includes: cooling a solution of Trypan Blue; and filtering the cooled solution. In another example, a method includes: mixing a water-soluble polymer with a Trypan Blue solution. The method may further include adding one or more ingredients such as an aqueous buffer, an osmolyte, an acid, a base, a buffer, a cell culture medium, water, or combinations thereof.

The present invention concerns the use of light to convert indicant to indigo. The invention is particularly useful in dyeing textiles from indican by simple light exposure, thereby providing a greener alternative to current industrial processes for colored fabrics and other products.

The present invention provides a composition comprising indigo carmine and a copper (II) metal ion or a salt or hydrate thereof, wherein the composition has a CD value of 1.5 and a pH5. The present invention significantly increases the shelf-life of aqueous indigo carmine formulations at pH5 without requiring special filling or storage conditions to physically remove oxygen from the system. In doing so, aqueous solutions comprising indigo carmine dye are stabilized and suitable for use in, for example, colorized disinfection systems.