title: Theming in React / Styled Component
body: <p>everyone. My issue is very basic. but I could not find what is wrong.</p>
  <pre><code>//theme.js
  
  export const lightTheme = {
    mode: 'light',
    PRIMARY_BACKGROUND_COLOR: '#ffefd5',
    PRIMARY_TEXT_COLOR: '#DB7093',
    SECONDARY_TEXT_COLOR: '#333333',
    PRIMARY_BUTTON_COLOR: '#b9d6f3',
    SECONDARY_BUTTON_COLOR: '#a1c9f1',
  };
  
  </code></pre>
  <pre><code>// style.js
  
  export const GView = styled.View`
    flex: 1;
    background: ${props =&gt; props.theme.PRIMARY_BACKGROUND_COLOR};
  `;
  </code></pre>
  <pre><code>//ERROR
  
  Failed to parse declaration &quot;background: &quot;
  </code></pre>
  <ol>
  <li>when use string, got error.</li>
  <li>when use hex, works well.</li>
  </ol>
  <p>Thanks.</p>