This is the 18498th most frequent Russian word.
яркость
Brightness.
Here, 'яркость' is used to describe the intensity or luminance of the light in the room.
Яркость света в комнате была очень высокой.
The brightness of the light in the room was very high.
In this context, 'яркость' describes the vividness or striking quality of the color or appearance of the dress.
Её платье выделялось своей яркостью и свежестью.
Her dress stood out for its brightness and freshness.
Here, 'яркость' metaphorically refers to the 'brilliance' or distinctiveness of his ideas.