Add documentation for recently added color properties

README.md

@@ -3,4 +3,37 @@
 This is a plugin for [Kaleidoscope][fw], that adds a NumPad-specific LED
 effect, along with a way to toggle to a numpad layer, and apply the effect.
 
+## Using the extension
+
+To use the plugin, include the header, and tell the firmware to use it:
+
+```c++
+#include "Kaleidoscope-NumPad.h"
+
+KALEIDOSCOPE_INIT_PLUGINS(NumPad);
+
+void setup() {
+  Kaleidoscope.setup();
+
+  NumPad.color = CRGB(0, 0, 160); // a blue color
+  NumPad.lock_hue = 85; // green
+}
+```
+
+##   Plugin methods
+
+The plugin provides the `NumPad` object, with the following properties:
+
+### `.color`
+
+> This property sets the color that the NumPad keys are highlighted in.
+>
+> The default is `CRGB(160, 0, 0)`, a red color.
+
+### `.lock_hue`
+
+> This property sets the color hue that the NumLock LED breathes in.
+>
+> The default is `170`, a blue hue.
+
  [fw]: https://github.com/keyboardio/Kaleidoscope