This template returns colour codes (in hex format) for use in graphs.
((graph color|1))
→ #1F78B4 ((graph color|2))
→ #33A02C ((graph color|3))
→ #E31A1C ((graph color|20|18))
→ #E31A1C ((graph color|cont=y|50|0|100))
→ #7f7f7f