Hello Sarah - though it is not possible to provide a "stripy color" for a particular dimensional value, you can however provide a custom color if you wanted a value to stand out - by using the color by expression option in the properties panel.
(providing this information for those that come across this type of question and wondering how to color by formula / expression)
For example - you can us the following with HTML color names
pick(match("OICA region", 'Africa', 'Americas', 'AOME', 'Europe'), 'springgreen', 'lightskyblue', 'violet', 'lightsalmon' )
or an appropriate RGB value - using rgb(255,255,255,) - for example.
I used this in the screen shot below
Hope this is helpful - in case you need it.