You can customize the tabbed pages by creating new styles in TabbedPage.Resources and define styles to the tabs.
XAML
<TabbedPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:MultiseletionSample"
x:Class="MultiseletionSample.MainPage">
<TabbedPage.Resources>
<Style TargetType="local:NewPage1" x:Key="style">
<Setter Property="BackgroundColor" Value="Blue" />
</Style>
</TabbedPage.Resources>
<local:NewPage1 Title="New" Style="{StaticResource style}"/>
<local:NewPage2 Title="New" Style="{StaticResource style}"/>
<local:NewPage3 Title="New" Style="{StaticResource style}"/>
</TabbedPage>
Share with