CAD tip # 4497:
Question
In AutoCAD, use the COLOR command, choose the Color books tab, select e.g. the "RAL CLASSIC" book and read the "RGB equivalent" values.
In Inventor (9,10,11...) choose Format - Style Editor - Color and set the "Diffuse" component (for Ambient and Emissive choose black, for Specular choose white). Click on the Diffuse pane, choose Define Custom Colors and enter the RGB values found in AutoCAD (the 0-255 range).
In higher versions, you can also import the RAL_Colors.styxml file containing the RAL palette for the Style editor, or a separate RAL .AdskLib material/appearance library (.adsklib will add RAL materials to Inventor, Revit, AutoCAD and other Autodesk software) - see Download.
Do not forget to attach the RAL library to your project (right-click on the library node to add new):

