Thanks for contacting Syncfusion Support,
We request you to refer the below the documentation link for how to customize the font size and color in Syncfusion Blazor components
We also have a theme studio application to customize color for Syncfusion Components. Our theme studio is used for customizing your own theme from an existing theme. It also supports to generate styles for specific controls that you want to customize. Please refer the theme studio application link and documentation link
Please get back to us if you need any further assistance on this.
Jesus Arockia Sankaran S