Updated Brushes (markdown)

Brushes.md

@@ -142,4 +142,26 @@ local spotlight = Brushes.GetRadialGradientBrush(colors, 0.5, 0.5, 0, 0);
 Drawing the first brush would look like this:  
 ![RadialGradientBrush](http://i.imgur.com/GXkooQt.png "RadialGradientBrush")  
 Drawing the second brush would look like this:  
-![RadialGradientBrush](http://i.imgur.com/PpMjgnq.png "RadialGradientBrush")
+![RadialGradientBrush](http://i.imgur.com/PpMjgnq.png "RadialGradientBrush")
+
+---
+### GetRelativeColor
+Returns the color at the given position in a gradient.
+#### Syntax:
+```lua
+color GetRelativeColor(table gradientColors, double position);
+```
+##### Required arguments
+- **gradientColors:** A table using colors as keys and doubles as offsets
+- **position:** A position between 0 and 1.
+
+#### Example:
+```lua
+-- Create a table and add keys to it (the color) and values (the offset).
+local colors = {};
+colors[Brushes.GetColor(255, 255, 0, 0)] = 0;      -- red
+colors[Brushes.GetColor(255, 255, 255, 0)] = 1;    -- yellow
+
+-- Get the color that is in the middle of the gradient, between red and yellow
+local orange = Brushes.GetRelativeColor(colors, 0.5);
+```