butter yellow

Short definition from Wiktionary

Noun

1. 1
   A light, soft yellow colour.
2. 2
   An azo dye with the formula C₆H₅N₂C₆H₄N(CH₃)₂, used as a food additive in butter and margarine before its toxicity was recognized.

Adjective

1. 1
   Having a light, soft yellow colour.