The performance of a super-resolution fluorescence depletion microscope system depends crucially on the precise alignment of the pump and erase beams with the axis of the focusing objective. Here, we propose a new design method for a two-color spiral phase plate with a single-layer structure (S2SPP), and we experimentally investigate the image properties given by the phase plate. In spite of its simple structure, the plate can provide a super-resolution image with a spatial resolution better than 70 nm. Beside eliminating alignment problems and yielding a compact setup, the simplicity of fabrication of the S2SPP makes our proposed method very suitable for commercial microscope systems.