ΔE 7.6, close: similar, with a visible difference side by side. Skyshard is a little lighter, more muted than Hellblau RLM 65.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Skyshard is a little lighter, more muted than Hellblau RLM 65.
The same difference applies the other way round: Hellblau RLM 65 is a little darker, more saturated.
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 Hellblau RLM 65 on the colour wheel See Skyshard on the colour wheel
All matches: Hellblau RLM 65 equivalents · Skyshard equivalents