We propose and demonstrate a photonic spectral processor for applying arbitrary spectral phase and amplitude at high resolution with a 100-GHz free-spectral range for colorless wavelength-division-multiplexing adaptive filtering applications. The system employs free-space optics for projecting the dispersed light coming out of a planar-lightwave circuit onto a phase spatial-light modulator. The processor achieves 3-GHz optical resolution over 75-GHz usable bandwidth, with 557-MHz addressable granularity.