This is the 5416th most frequent Polish word.
subtelny
"Subtelny" means "subtle" or "delicate" in English.
Here, 'subtelne' describes the nuances in color, meaning they are delicate and not immediately noticeable.
Obraz miał bardzo subtelne odcienie niebieskiego.
The painting had very subtle shades of blue.
In this sentence, 'subtelne' refers to the remarks being made in a way that is not overt, but meaningful and tactful.
Jego subtelne uwagi pomogły mi poprawić projekt.
His subtle remarks helped me improve the project.
'Subtelny' here describes the smell, indicating it is faint and gentle, not overpowering.