To reproduce: 
1. Drag and drop RadMenu on form. 
2. Add few items
3. Set design time the ForeColor of of RadMenuItem to red.  The ForeColor is changed.
4. Run the form and you will see that the ForeColor of RadMenuItem is black again. 

Workaround:  
1. Set the ForeColor run time using following code  snippet: 
this.radMenuItem1.ForeColor = Color.Red;
 
2. Set the ForeColor of TextPrimitive through Element hierarchy editor. You can see the DesignTimeSetForeColorOfRadMenuItem.png image how to set it.