We perform a series of computer simulations and optical experiments for multiple-wavelength ptychographic imaging to analyze the relationship between the imaging quality and the magnitude of wavelength. Two kinds of samples including the grating-like and the biological sample are tested. Our experimental results are highly consistent with simulations, demonstrating the feasibility and effectiveness of the multiple-wavelength ptychography. Compared with the single-wavelength ptychographic imaging, it can achieve very good imaging quality with a fast speed of iterative convergence and a high robustness to the noises in the case of multiple-wavelengh ptychography. In addition, optical experiments also reveal that with the magnitude of wavelength increasing, the complexity of the ptychographic system is grown up within increased noises and errors, which causes the imaging quality to keep no enhancement or even to get worse. For our concrete configuration in this paper, with a simple digital procedure for noise depressing, the best results may be obtained for the case of dual-wavelength. Furthermore, it implies that there is an optimized condition for multiple-wavelength ptychography. We find that it requires mainly analyzing the balance between the multiple-wavelength-benefited noise-resistance and the systematic complexity for the optimized condition, which may be really important and meaningful for the practical utilizing of multiple-wavelength ptychography.