Docs: Add description of the different lineage color options

phylogenetic/defaults/description.md

@@ -13,4 +13,26 @@ We curate sequence data and metadata from NCBI as starting point for our analyse
 * [data.nextstrain.org/files/workflows/dengue/sequences_denv4.fasta.zst](https://data.nextstrain.org/files/workflows/dengue/sequences_denv4.fasta.zst)
 * [data.nextstrain.org/files/workflows/dengue/metadata_denv4.tsv.zst](https://data.nextstrain.org/files/workflows/dengue/metadata_denv4.tsv.zst)
 
-For more information about the dengue lineage system, to submit questions, or lineage proposals; please visit [dengue-lineages.org](https://dengue-lineages.org/). 
+
+### Lineage coloring
+
+There are up to six different lineage coloring options available depending on the source of data:
+
+**Based on a Nextclade call against [community/v-gen-lab/dengue datasets](https://github.com/nextstrain/nextclade_data/tree/master/data/community/v-gen-lab/dengue).**
+
+The lineage color options are split into levels of detail, with an example shown beside each level:
+
+* **Genotype (Nextclade):** 3III
+* **Major Lineage (Nextclade):** 3III_B
+* **Minor Lineage (Nextclade):** 3III_B.3.2
+
+For more information about the dengue lineage system please visit [dengue-lineages.org](https://dengue-lineages.org/).
+
+**Based on NCBI GenBank metadata**
+
+* **Serotype (GenBank metadata):** denv1 to denv4
+
+**Based on Augur clade assignment (`clade_membership`)**
+_(Only available for genome trees, not gene trees)_
+* **Serotype (Nextstrain):** DENV1 – DENV4, annotated only on the "all" tree
+* **Genotype (Nextstrain):** such as DENV3/III  _(equivalent to 3III in "Genotype (Nextclade)")_, annotated only on the serotype-specific trees.