style Attribute

This is CSS in JavaScript also called React Style.
Notice the double curly brackets
Notice the attribute names are slightly different, no dashes.

index.jsx

const Button = () => { 
   return <button style = {{ backgroundColor : 'red' }}>My Button</button>  
} 

const Button = () => { 
   const button_style = { 
      backgroundColor : 'red'  
   } 
   return <button style={button_style}>My Button</button> 
} 

Using a property as part of the style

const Button = () => { 
   const button_style = { 
      backgroundColor : prop_ 
   } 
   return <button style={button_style}>My Button</button> 
}