Cobalt blue on cool, soft skin tones (True Summer)

The answer

Close, but not a match. Cobalt blue sits just outside the True Summer palette. The nearest thing in the palette is #3E6B8C, ΔE 12.4 away. Under 12 reads as the same colour family; past 25 the two are visibly different colours.

It does not collide with anything on the season's avoid list, so the only question is distance.

How cobalt blue scores across all twelve seasons

Cobalt blue is an opinionated colour: True Winter scores it 92 and Light Spring scores it 0. A gap that wide means the colour genuinely decides something, and getting it right is worth the effort.

True Summer sits 4 of twelve at 69, 23 points behind True Winter. That gap is the honest size of the compromise, not a verdict on the colour.

• True Winter: 92 (ΔE 3.2).
• Bright Winter: 79 (ΔE 8.5).
• Deep Winter: 74 (ΔE 10.3).
• True Summer: 69 (ΔE 12.4) <- this season.
• Light Spring: 0 (ΔE 43.8).

What to wear instead

Nearest first. These are the colours in the True Summer palette that get closest to what you wanted from cobalt blue, so the substitution costs the least.

• #3E6B8C: deep, nearest common name cobalt blue (ΔE 12.4).
• #3E4A5A: deep, a charcoal (ΔE 8.2).
• #5578A0: mid-tone, nearest common name cobalt blue (ΔE 16.4).