app/models/group.rb

@@ -13,6 +13,20 @@ class Group < ApplicationRecord
 
   has_many :guests
 
+  def colorize_children(generation = 1)
+    derived_colors = generation == 1 ? color.paint.palette.analogous(size: children.count) : color.paint.palette.decreasing_saturation
+
+    children.zip(derived_colors) do |child, raw_color|
+
+      final_color = raw_color.paint
+      final_color.brighten(60) if final_color.dark?
+
+      child.update!(color: final_color)
+
+      child.colorize_children(generation + 1)
+    end
+  end
+
   private
 
   def set_color

config/initializers/colors.rb

@@ -0,0 +1,6 @@
+Chroma.define_palette :decreasing_saturation do
+  spin(20).desaturate(40)
+  spin(-20).desaturate(40)
+  spin(40).desaturate(40)
+  spin(-40).desaturate(40)
+end

db/seeds.rb

@@ -65,3 +65,7 @@ NUMBER_OF_GUESTS.times do
 end
 
 ActiveJob.perform_all_later(3.times.map { TableSimulatorJob.new })
+
+'red'.paint.palette.triad(as: :hex).zip(Group.roots).each { |(color, group)| group.update!(color: color.paint.desaturate(40)) }
+
+Group.roots.each(&:colorize_children)