Nucleotide Ambiguity Colours
| A | Adenine |
| C | Cytosine |
| G | Guanine |
| T | Thymine |
| U | Uracil |
| I | Inosine |
| X | Xanthine (sometimes Unknown) |
| R | Unknown Purine |
| Y | Unknown Pyrimidine |
| W | Weak nucleotide (A or T) |
| S | Strong nucleotide (G or C) |
| M | Amino (A or C) |
| K | Keto (G or T) |
| B | Not A (G or C or T) |
| H | Not G (A or C or T) |
| D | Not C (A or G or T) |
| V | Not T (A or G or C) |
| N | Unknown |