[cssom] Resolved value for <color> properties should be used value

Fixes #566.

cssom/Overview.bs

@@ -2682,11 +2682,24 @@ remain the same for compatibility with deployed scripts. To address this
 issue this specification introduces the concept of a
 <dfn>resolved value</dfn>.
 
-The <a>resolved value</a> for a given property can be determined
+The <a>resolved value</a> for a given longhand property can be determined
 as follows:
 
 <dl class="switch">
+ <dt>'background-color'
+ <dt>'border-block-end-color'
+ <dt>'border-block-start-color'
+ <dt>'border-bottom-color'
+ <dt>'border-inline-end-color'
+ <dt>'border-inline-start-color'
+ <dt>'border-left-color'
+ <dt>'border-right-color'
+ <dt>'border-top-color'
+ <dt>'box-shadow'
+ <dt>'caret-color'
+ <dt>'color'
  <dt>'line-height'
+ <dt>'outline-color'
  <dd>The <a>resolved value</a> is the <a>used value</a>.
 
  <dt>'block-size'
@@ -2700,7 +2713,6 @@ as follows:
  <dt>'margin-left'
  <dt>'margin-right'
  <dt>'margin-top'
- <dt>'margin'
  <dt>'padding-block-end'
  <dt>'padding-block-start'
  <dt>'padding-bottom'
@@ -2709,7 +2721,6 @@ as follows:
  <dt>'padding-left'
  <dt>'padding-right'
  <dt>'padding-top'
- <dt>'padding'
  <dt>'width'
  <dd>If the property applies to the element or pseudo-element and the <a>resolved value</a> of the
  'display' property is not ''display/none'' or ''display/contents'', then the <a>resolved value</a>