diff --git a/Readme.md b/Readme.md
index a2fed76..38af856 100644
--- a/Readme.md
+++ b/Readme.md
@@ -14,23 +14,36 @@ the system appearance mode (only macOS).
 ### Example program (simple button):
 ```python
 import tkinter
-import customtkinter
+import customtkinter  # <- import the CustomTkinter module
 
-root_tk = tkinter.Tk()
+customtkinter.set_appearance_mode("Light")  # Other: "Dark", "System" (only macOS)
+
+root_tk = tkinter.Tk()  # create the Tk window like you normally do
 root_tk.geometry("400x240")
 root_tk.title("CustomTkinter Test")
 
 def button_function():
     print("button pressed")
 
+# Use CTkButton instead of tkinter Button
 button = customtkinter.CTkButton(master=root_tk, corner_radius=10, command=button_function)
 button.place(relx=0.5, rely=0.5, anchor=tkinter.CENTER)
 
 root_tk.mainloop()
 ```
 which gives the following:
+
 ![](documentation_images/simple_button_test.png)
 
+### Use custom colors and shapes:
+If you dont specify any colors, customtkinter uses the standard blue color in the light theme.
+You can change the color theme to dark by calling
+```customtkinter.set_appearance_mode("Dark")```.
+If you specify custom colors for CustomTkinter elements, the you can either use a
+tuple in the form: (light_color, dark_color). Or you can set a single color
+which will be used in light and dark theme.
+
+
 ### How to use macOS dark mode?
 If you have a python version with Tcl/Tk >= 8.6.9, then you can enable the macOS
 darkmode. Currently only the anaconda python versions have Tcl/Tk >= 8.6.9.
@@ -45,6 +58,10 @@ customtkinter.set_appearance_mode("System")
 
 customtkinter.disable_macos_darkmode()
 ```
+which gives the following with the above simple button program:
+
+![](documentation_images/simple_macOS_darkmode_test.png)
+
 
 ## Ui-Elements
 
diff --git a/customtkinter/customtkinter_color_manager.py b/customtkinter/customtkinter_color_manager.py
index cd8603f..fe11d2b 100644
--- a/customtkinter/customtkinter_color_manager.py
+++ b/customtkinter/customtkinter_color_manager.py
@@ -1,3 +1,4 @@
+import sys
 
 
 class CTkColorManager:
@@ -25,5 +26,5 @@ class CTkColorManager:
         elif main_color.lower() == "blue":
             cls.set_theme_color("#1C94CF", "#5FB4DD")
 
-        elif main_color.lower() == "blue":
-            cls.set_theme_color("#1C94CF", "#5FB4DD")
+        else:
+            sys.stderr.write("WARNING (CTkColorManager): No such color theme available: {}\n".format(main_color))
diff --git a/documentation_images/simple_button_test.png b/documentation_images/simple_button_test.png
index e4d7606..b3e0d21 100644
Binary files a/documentation_images/simple_button_test.png and b/documentation_images/simple_button_test.png differ
diff --git a/documentation_images/simple_macOS_darkmode_test.png b/documentation_images/simple_macOS_darkmode_test.png
new file mode 100644
index 0000000..c9ed78e
Binary files /dev/null and b/documentation_images/simple_macOS_darkmode_test.png differ
diff --git a/simple_test.py b/simple_test.py
index d58b334..122b119 100644
--- a/simple_test.py
+++ b/simple_test.py
@@ -42,6 +42,8 @@
 import tkinter
 import customtkinter
 
+customtkinter.enable_macos_darkmode()
+
 root_tk = tkinter.Tk()
 root_tk.geometry("250x150")
 root_tk.title("CustomTkinter Test")