Add ability to turn off coloring

lib/tty/pie_chart.rb

@@ -74,7 +74,7 @@ def data_items
         angle = percent * FULL_CIRCLE_DEGREES / 100.to_f
         color_fill = item[:fill] || fill
         DataItem.new(item[:name], item[:value], percent, angle,
-                     item[:color], color_fill)
+                     item.fetch(:color, false), color_fill)
       end
     end
 
@@ -116,11 +116,15 @@ def draw
         output << ' ' * (center_x - width) if top.nil?
         (-width..width).each do |x|
           angle = radian_to_degree(Math.atan2(x, y))
-          idx = select_data_item(angle, angles)
+          item = items[select_data_item(angle, angles)]
           if !top.nil?
             output << cursor.move_to(center_x + x, center_y + y)
           end
-          output << @pastel.decorate(items[idx].fill, items[idx].color)
+          if item.color
+            output << @pastel.decorate(item.fill, item.color)
+          else
+            output << item.fill
+          end
         end
 
         if legend

lib/tty/pie_chart/data_item.rb

@@ -37,7 +37,8 @@ def initialize(name, value, percent, angle, color, fill)
       # @api private
       def to_label
         percent_fmt = '%.2f' % percent
-        "#{@pastel.decorate(fill, color)} #{name} #{percent_fmt}%"
+        label = color ? @pastel.decorate(fill, color) : fill
+        "#{label} #{name} #{percent_fmt}%"
       end
     end
   end # PieChart

spec/unit/color_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+RSpec.describe TTY::PieChart, ':color option' do
+  it "draws a pie chart without colors" do
+    data = [
+      { name: 'BTC', value: 5977, fill: '*' },
+      { name: 'BCH', value: 3045, fill: '+' },
+      { name: 'LTC', value: 2030, fill: 'x' }
+    ]
+    pie = TTY::PieChart.new(data, radius: 2)
+
+    output = pie.draw
+
+    expect(output).to eq([
+      "   x**       * BTC 54.08%\n",
+      " +xx****\n",
+      "++++*****    + BCH 27.55%\n",
+      " +++****\n",
+      "   +**       x LTC 18.37%\n"
+    ].join)
+  end
+end