Rails Validate has_many Through on a wicked wizard form

I'm trying to validate a product form with has many through colors and sizes on a multi-step wicked wizard form using this gem enter link description here

but did not validate the step, someone have any idea how to validate related models on a wizard form? thank's

i've trying to validate through color model. but in this case scenario seems that is just possible through the product model.

class Product < ActiveRecord::Base

 has_many :sizeships
  has_many :sizes, through: :sizeships
  has_many :colorships
  has_many :colors, through: :colorships


 include Wicked::Wizard::Validations

    def self.wizard_steps
        [
            "first"
          ]
    end
end





class Color < ActiveRecord::Base
  attr_accessible :name, :hex


  has_many :colorships
  has_one :colorship
  has_many :products, :through => :colorships

  accepts_nested_attributes_for :products, :order

  include Wicked::Wizard::Validations

  def current_step
    product.current_step 
  end


  def wizard_steps
    Product.wizard_steps
  end

  def color_id_validations
    {

      color_id: {
        presence: {
          presence: true      }
      }
    }
  end

end