S₁₀₀/S₂₄ vs. S₁₆/S₈ colour − colour diagram for the whole GOODS-H sample in GOODS-N with 16   μm detection (black circles). Circles filled with green and orange colour are sources with S₁₀₀/S₂₄  >  43 at 0.2 < z < 0.6 and 1.0 < z < 1.7, respectively. Vertical and horizontal red lines indicate a cut off ratio of S₁₆/S₈  >  4 and S₁₀₀/S₂₄  >  43. We see that this diagram can serve as a redshift diagnostic, for sources at 1.0 < z < 1.7.