Both Uses of

contrast
in
The Hound of the Baskervilles

There could not have been a greater contrast between brother and sister, for Stapleton was neutral tinted, with light hair and gray eyes, while she was darker than any brunette whom I have seen in England--slim, elegant, and tall.
Chpt 7 *

contrast = difference

There is something tropical and exotic about her which forms a singular contrast to her cool and unemotional brother.
Chpt 8

contrast = an unmissable difference when compared side-x-side

Definitions:

(1) (contrast as in: contrast their writing styles)
point to differences between; or compare to show differences
(2) (contrast as in: there is a contrast)
a difference -- especially a notable difference; or the side-x-side arrangement of things that draws attention to an unmissable difference
(3) (contrast as in: sharpen the picture contrast)
the difference between tones of an image -- as in a photo or video -- such as the quality of brightness or the intensity of shades or colors