Abolish restrictions governing colour choices (#4978)

CONTRIBUTING.md

@@ -171,9 +171,6 @@ Please do this in a community forum or repository used and known by the wider co
 Once you've received consensus that the community is happy with your proposed color change, please feel free to open a PR making the change and link to the public discussion where this was agreed by the community.
 If there are official branding guidelines to support the colour choice, please link to those too.
 
-Please note that Linguist currently implements a [color proximity test][] to ensure colors are sufficiently different from one another so you may not be able to use the precise color you want - reds and blues are really popular.
-As such, we recommend you test the color change locally before making your plea to the wider language community.
-
 ## Testing
 
 You can run the tests locally with:
@@ -245,7 +242,6 @@ If you are the current maintainer of this gem:
 [languages]: /lib/linguist/languages.yml
 [licenses]: https://github.com/github/linguist/blob/257425141d4e2a5232786bf0b13c901ada075f93/vendor/licenses/config.yml#L2-L11
 [new-issue]: https://github.com/github/linguist/issues/new
-[color proximity test]: https://github.com/github/linguist/blob/master/test/test_color_proximity.rb
 [samples]: /samples
 [search-example]: https://github.com/search?utf8=%E2%9C%93&q=extension%3Aboot+NOT+nothack&type=Code&ref=searchresults
 [gpr]: https://help.github.com/en/articles/configuring-rubygems-for-use-with-github-package-registry

github-linguist.gemspec

@@ -30,7 +30,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'pry'
   s.add_development_dependency 'rake'
   s.add_development_dependency 'yajl-ruby'
-  s.add_development_dependency 'color-proximity', '~> 0.2.1'
   s.add_development_dependency 'licensed', '~> 2.0'
   s.add_development_dependency 'licensee'
   s.add_development_dependency 'bundler', '>= 1.10'

test/helper.rb

@@ -2,7 +2,6 @@
 require "minitest/autorun"
 require "mocha/minitest"
 require "linguist"
-require 'color-proximity'
 require "linguist/blob"
 require 'licensee'
 

test/test_language.rb

@@ -470,14 +470,6 @@ def test_all_popular_languages_exist
     assert missing.empty?, message
   end
 
-  def test_no_unused_colours
-    Language.all.each do |language|
-      next unless language.type == :data || language.type == :prose ||
-        language.group.to_s != language.name
-      assert !language.color, "Unused colour assigned to #{language.name}"
-    end
-  end
-
   def test_non_crash_on_comma
     assert_nil Language[',']
     assert_nil Language.find_by_name(',')