Hi

To do that you should edit the control template of menu item. When you edit the control template you have many options to remove the mouse over behavior, but may be the easiest way is to remove actions applied in MouseOver and  Highlighted visual states.  Below is a snippet of this.

  <VisualState x:Name="MouseOver">

    <!--<Storyboard x:Name="MouseOverStoryboard" >

        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="SelectedIndicator" Storyboard.TargetProperty="Visibility">

            <DiscreteObjectKeyFrame KeyTime="0">

               <DiscreteObjectKeyFrame.Value>

                   <Visibility>Visible</Visibility>

               </DiscreteObjectKeyFrame.Value>

            </DiscreteObjectKeyFrame>

        </ObjectAnimationUsingKeyFrames>

    </Storyboard>-->

  </VisualState>

  <VisualState x:Name="Highlighted">

    <!--<Storyboard >

        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="HighlightedIndicator" Storyboard.TargetProperty="Visibility">

            <DiscreteObjectKeyFrame KeyTime="0">

                <DiscreteObjectKeyFrame.Value>

                    <Visibility>Visible</Visibility>

                </DiscreteObjectKeyFrame.Value>

            </DiscreteObjectKeyFrame>

        </ObjectAnimationUsingKeyFrames>

    </Storyboard>-->

  </VisualState>

And finaly you should aplly this new control template by MenuItem style:

 <ig:XamMenu ItemContainerStyle="{StaticResource MenuItemStyle}">

            <Button Content="Button" />

            <Button Content="Button"/>

            <Button Content="Button" />

        </ig:XamMenu>

Only one note in our new release 10.2 XamWebMenuItem and XamWebMenu are renamed, as  the ‘Web’ prefix is removed. So the code snippets are with new names, but the approach describe here works and in old releases.

I have attached the full xaml page with the new control template in this post