ΔE 7.2, close: similar, with a visible difference side by side. Payne's Gray is warmer than Thunderhawk Blue. They are different kinds of paint: Citadel Thunderhawk Blue is an opaque base/layer paint and Golden Payne's Gray is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Payne's Gray is warmer than Thunderhawk Blue. They are different kinds of paint.
The same difference applies the other way round: Thunderhawk Blue is cooler.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Thunderhawk Blue on the colour wheel See Payne's Gray on the colour wheel
All matches: Thunderhawk Blue equivalents · Payne's Gray equivalents