DRY up Color model validations

app/models/color.rb

@@ -38,9 +38,8 @@ class Color < ApplicationRecord
            dependent: :nullify
 
   validates :name, :hexcode, presence: true
-
-  validates :name, length: { maximum: 255, unless: lambda { |e| e.name.blank? } }
-  validates :hexcode, format: { with: /\A#[0-9A-F]{6}\z/, unless: lambda { |e| e.hexcode.blank? } }
+  validates :name, length: { maximum: 255 }
+  validates :hexcode, format: { with: RGB_HEX_FORMAT, allow_blank: true }
 
   normalizes :hexcode, with: ::Colors::HexColor::Normalizer
 end

app/models/colors/hex_color.rb

@@ -30,6 +30,9 @@
 
 module Colors
   module HexColor
+    RGB_HEX_FORMAT = /\A#[0-9A-F]{6}\z/
+    private_constant :RGB_HEX_FORMAT
+
     ##
     # Get the fill style for this color.
     # If the color is light, use a dark font.

app/models/design_color.rb

@@ -43,9 +43,9 @@ class DesignColor < ApplicationRecord
     end
   end
 
+  validates :variable, :hexcode, presence: true
   validates :variable, uniqueness: true
-  validates :hexcode, :variable, presence: true
-  validates :hexcode, format: { with: /\A#[0-9A-F]{6}\z/, unless: lambda { |e| e.hexcode.blank? } }
+  validates :hexcode, format: { with: RGB_HEX_FORMAT, allow_blank: true }
 
   normalizes :hexcode, with: ::Colors::HexColor::Normalizer