Hi there,
You can set the colors of buttons using the BackgroundColor or TextColor properties. If you would like to set the font of a button's text, use the property FontTypeface (options: default, serif, sans serif, monospace).
For your question for 3D buttons, see this topic.
If you would like to add an icon to a button, use this link in Thunkable here.
https://community.thunkable.com/t/free-button-addon-extension/9790
You would also want to search the extensions directory Pura Vida Apps Extensions, which has many extensions related to buttons.