Salts of ATP can be isolated as colorless solids.
ATP is stable in aqueous solutions between pH 6.8 and 7.4 (in the absence of catalysts).  At more extreme pH levels, it rapidly hydrolyses to ADP and phosphate. Living cells maintain the ratio of ATP to ADP at a point ten orders of magnitude from equilibrium, with ATP concentrations fivefold higher than the concentration of ADP. In the context of biochemical reactions, the P-O-P bonds are frequently referred to as high-energy bonds.