has_attached_file(
  :avatar,
  :styles => { :large => "300x300", :small => "100x100" },
  :convert_options => { all => "-colorspace RGB" }
)

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

Convert colorspace of images attached with Paperclip