The effect of tensile stress upon the optical properties of organic dye molecules has been investigated using semi-empirical methods (AM1, INDO/S). It is found that some of the dyes exhibit significant changes of absorption wavelengths and/or oscillator strengths, which renders them suitable for mechanochromic single molecule experiments. The changes can be explained on the basis of the relevant frontier orbitals and the structural changes of the dyes upon exertion of tensile stress,