Hi chandran85965395
You can use the long description with inline styles or the theme editor to set the css of the message to your requirements:
Inline CSS properties for adaptive form components
Adobe Experience Manager Help | Themes in AEM Forms
They are pretty intuitive - go to the edit dropdown in the top right and change to style, then click on the textbox or other widget, then long description. Change something obvious like the text colour to get a feel for it.
Use the theme editor if you want to apply the same look and feel across more than one form and then override it on a form by form basis with inline styles if you need to.