message: Update color variables used in UnderlineNav
diff: @@ -14,7 +14,7 @@ const SELECTED_CLASS = 'selected'
  const UnderlineNavBase = styled.nav`
  display: flex;
  justify-content: space-between;
  - border-bottom: 1px solid #eaecef;
  + border-bottom: 1px solid ${get('colors.border.secondary')};
  &.UnderlineNav--right {
  justify-content: flex-end;
  @@ -75,29 +75,29 @@ const UnderlineNavLink = styled.a.attrs<StyledUnderlineNavLinkProps>(props => ({
  margin-right: ${get('space.3')};
  font-size: ${get('fontSizes.1')};
  line-height: ${get('lineHeights.default')};
  - color: ${get('colors.gray.6')};
  + color: ${get('colors.underlinenav.text')};
  text-align: center;
  border-bottom: 2px solid transparent;
  text-decoration: none;
  &:hover,
  &:focus {
  - color: ${get('colors.gray.9')};
  + color: ${get('colors.underlinenav.textHover')};
  text-decoration: none;
  - border-bottom-color: ${get('colors.gray.2')};
  + border-bottom-color: ${get('colors.border.tertiary')};
  transition: 0.2s ease;
  .UnderlineNav-octicon {
  - color: ${get('colors.gray.5')};
  + color: ${get('colors.text.tertiary')};
  }
  }
  &.selected {
  - color: ${get('colors.gray.9')};
  - border-bottom-color: ${get('colors.accent')};
  + color: ${get('colors.underlinenav.textActive')};
  + border-bottom-color: ${get('colors.underlinenav.borderActive')};
  .UnderlineNav-octicon {
  - color: ${get('colors.gray.5')};
  + color: ${get('colors.underlinenav.iconActive')};
  }
  }
  