diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3cc1490..6bfc9f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+1.0.0
+-----
+
+- Adjust to avoid lighter colors.
+- Avoid continuous chars have same color.
+- Use same color for each chars in :black_white mode.
+
 0.5.1
 -----
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 705b67f..ec66969 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rucaptcha (0.5.1)
+    rucaptcha (1.0.0)
       railties (>= 3.2)
 
 GEM
diff --git a/lib/rucaptcha/captcha.rb b/lib/rucaptcha/captcha.rb
index 18a646f..1687f8b 100644
--- a/lib/rucaptcha/captcha.rb
+++ b/lib/rucaptcha/captcha.rb
@@ -5,19 +5,17 @@ module RuCaptcha
     class << self
       def random_color
         if RuCaptcha.config.style == :colorful
-          color = [random_color_seed, random_color_seed, random_color_seed]
-          color[rand(3)] = 0.to_s(8)
+          color1 = rand(56) + 15
+          color2 = rand(10) + 140
+          color = [color1, color2, rand(15)]
+          color.shuffle!
           color
         else
-          color_seed = rand(50).to_s(8)
+          color_seed = rand(40) + 10
           [color_seed, color_seed, color_seed]
         end
       end
 
-      def random_color_seed
-        (rand(150) + 10).to_s(8)
-      end
-
       def random_chars
         chars = SecureRandom.hex(RuCaptcha.config.len / 2).downcase
         chars.gsub!(/[0ol1]/i, (rand(8) + 2).to_s)
@@ -44,8 +42,23 @@ module RuCaptcha
         text_opts    = []
         line_opts    = []
 
+        rgbs = []
+        chars.count.times do |i|
+          color = random_color
+          if i > 0
+            preview_color = rgbs[i - 1]
+            # Avoid color same as preview color
+            if color.index(color.min) == preview_color.index(preview_color.min) &&
+               color.index(color.max) == preview_color.index(preview_color.max)
+              # adjust RGB order
+              color = [color[1], color[2], color[0]]
+            end
+          end
+          rgbs << color
+        end
+
         chars.each_with_index do |char, i|
-          rgb = random_color
+          rgb = RuCaptcha.config.style == :colorful ? rgbs[i] : rgbs[0]
           text_color = "rgba(#{rgb.join(',')}, 1)"
           line_color = "rgba(#{rgb.join(',')}, 0.6)"
           text_opts << %(-fill '#{text_color}' -draw 'text #{(text_left + text_width) * i + all_left},#{text_top} "#{char}"')
diff --git a/lib/rucaptcha/version.rb b/lib/rucaptcha/version.rb
index 03f518d..12a51a3 100644
--- a/lib/rucaptcha/version.rb
+++ b/lib/rucaptcha/version.rb
@@ -1,3 +1,3 @@
 module RuCaptcha
-  VERSION = '0.5.1'
+  VERSION = '1.0.0'
 end