This is the 14428th most frequent Russian word.
оттенком
"Оттенком" means "shade" or "nuance" in English.
Here, "оттенках" refers to variations or gradations of a color, specifically gray shades in the painting context.
Эта картина нарисована в серых оттенках.
This painting is drawn in shades of gray.
Here, "оттенком" is used metaphorically to describe a subtle variation in emotion conveyed by her warm voice.
Её голос отдавал теплым оттенком грусти.
Her voice carried a warm note of sadness.
Here, "оттенком" is describing a faint color variation, specifically a bluish tone in the fabric.