message: use themeGet
diff: import React from 'react'
  import PropTypes from 'prop-types'
  import styled from 'react-emotion'
  +import {themeGet} from 'styled-system'
  import {withSystemProps, COMMON} from './system-props'
  import {colors} from './theme'
  @@ -18,9 +19,11 @@ function textDecoration({nounderline}) {
  }
  }
  -function color({muted, scheme}) {
  +function color({muted, scheme, ...rest}) {
  return {
  - color: scheme === 'gray-dark' ? colors.gray[9] : muted || scheme === 'gray' ? colors.gray[6] : colors.blue[5]
  + color: scheme === 'gray-dark' ? themeGet('colors.gray.9', colors.gray[9])(rest)
  + : muted || scheme === 'gray' ? themeGet('colors.gray.6', colors.gray[6])(rest)
  + : themeGet('colors.blue.5', colors.blue[5])(rest)
  }
  }
  