Use standard colors for common values

[curran]

For example, these colors are semi-standardised in certain parts of UNHCR

• Drought rgb(247,148,29)
• Conflict/Insecurity rgb(231,100,106)
• Other rgb(160,123,94)
• Flood rgb(201,116,162)

HT @mugodavid

Related to https://github.com/unhcr/dataviz-styleguide/issues/63

[matthewsmawfield]

done