This study explores the luminescence properties of color centers in single-crystal diamond needles synthesized via chemical vapor deposition and their potential for all-optical sensing applications. The theoretical part is dedicated to the fundamentals of quantum sensing for different modalities, with the focus on all-optical approaches using diamond color centers. Current achievements and limitations are reviewed, and it is proposed to expand the diamond-based sensing platform by investigating color centers beyond the well-studied NV⁻ and SiV⁻ defects. The methodological part introduces a pipeline developed in this work for estimating the concentrations of NV charge states through spectral decomposition based on non-negative matrix factorization.