Woah, take's me back to late 80s computing when colors were few but paint programs all used to have patterns in them.
There's a really nice additive effect with patterns that can give a designer a way to show combinations of things together in a way that color really can't (bonus it's better for some visual impairments). For example, take a series of lines for one value:
\ \ \
\ \ \
\ \ \
and a series for another kind of value
/ / /
/ / /
/ / /
put them in the same visual space and simple add them together
x x x
x x x
x x x
You can also add in vertical, horizontal lines and even line width (and even line color over a baseline color) and you can encode a ton of different values into a single graphical area.
I used this technique to layer graph areas that overlap so you can still clearly see them even in black and white. Use a dot series to get a 3rd overlapping series you can see.
There's a really nice additive effect with patterns that can give a designer a way to show combinations of things together in a way that color really can't (bonus it's better for some visual impairments). For example, take a series of lines for one value:
and a series for another kind of value put them in the same visual space and simple add them together You can also add in vertical, horizontal lines and even line width (and even line color over a baseline color) and you can encode a ton of different values into a single graphical area.