Use this if you are using igraph from R
| categorical_pal {igraph} | R Documentation | 
This is a color blind friendly palette from https://jfly.uni-koeln.de/color/. It has 8 colors.
categorical_pal(n)
| n | The number of colors in the palette. We simply take the first
 | 
This is the suggested palette for visualizations where vertex colors mark categories, e.g. community membership.
A character vector of RGB color codes.
library(igraphdata)
data(karate)
karate <- karate 
  add_layout_(with_fr()) 
  set_vertex_attr("size", value = 10)
cl_k <- cluster_optimal(karate)
V(karate)$color <- membership(cl_k)
karate$palette <- categorical_pal(length(cl_k))
plot(karate)
Other palettes: 
diverging_pal(),
r_pal(),
sequential_pal()