noun, noun which may take the genitive case particle 'no'
dull yellow; mustard yellow
Describes a muted, subdued yellow color, often with a brownish or grayish tone. Used as a noun or with の to modify another noun.
The wall was painted a dull yellow.
She wore a mustard-yellow cardigan.
Compound of 鈍 (にぶ, 'dull') and 黄色 (きいろ, 'yellow'). The reading にぶきいろ reflects the rendaku voicing of きいろ to ぎいろ, which then becomes きいろ in this combination.