Pass alpha transparency up to the story
Pass alpha transparency up to the story

Fixes #802.

Instead of just passing `color.hex`, also pass the alpha value.
rhalff/storybook,storybooks/storybook,rhalff/storybook,storybooks/storybook,rhalff/storybook,storybooks/react-storybook,storybooks/react-storybook,storybooks/storybook,rhalff/storybook,storybooks/react-storybook,kadirahq/react-storybook,storybooks/react-storybook,kadirahq/react-storybook,rhalff/storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,storybooks/storybook,rhalff/storybook