Five candidates for the missing light colour, paired with the agreed core palette
Option 4 (#EDEEE9) as the primary light tone, paired with pure white (#FFFFFF) as a secondary snap colour for tight applications and reverse type.
Two-tone whites give flexibility: the soft sage-tinted white for large background fields, the pure white for type reverses and crisp detail. The slight green undertone in #EDEEE9 ties everything together without reading as creamy.