use color swatches for selected bg and fg in svg assets

common/gnome-shell/3.18/light-assets/misc/message-active.svg

@@ -2,11 +2,13 @@
 <!-- Created with Inkscape (http://www.inkscape.org/) -->
 
 <svg
+   xmlns:osb="http://www.openswatchbook.org/uri/2009/osb"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:cc="http://creativecommons.org/ns#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:svg="http://www.w3.org/2000/svg"
    xmlns="http://www.w3.org/2000/svg"
+   xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
    xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
    width="32"
@@ -17,7 +19,25 @@
    inkscape:version="0.91 r13725"
    sodipodi:docname="message-active.svg">
   <defs
-     id="defs6623" />
+     id="defs6623">
+    <linearGradient
+       id="selected_bg_color"
+       osb:paint="solid">
+      <stop
+         style="stop-color:#5294e2;stop-opacity:1;"
+         offset="0"
+         id="stop4137" />
+    </linearGradient>
+    <linearGradient
+       inkscape:collect="always"
+       xlink:href="#selected_bg_color"
+       id="linearGradient4139"
+       x1="16"
+       y1="1020.3622"
+       x2="16"
+       y2="1052.3622"
+       gradientUnits="userSpaceOnUse" />
+  </defs>
   <sodipodi:namedview
      id="base"
      pagecolor="#ffffff"
@@ -26,8 +46,8 @@
      inkscape:pageopacity="0.0"
      inkscape:pageshadow="2"
      inkscape:zoom="5.6"
-     inkscape:cx="28.080846"
-     inkscape:cy="10.089671"
+     inkscape:cx="-36.115583"
+     inkscape:cy="9.3753852"
      inkscape:document-units="px"
      inkscape:current-layer="layer1"
      showgrid="true"
@@ -58,7 +78,7 @@
      id="layer1"
      transform="translate(0,-1020.3622)">
     <rect
-       style="display:inline;opacity:1;fill:#5294e2;fill-opacity:1;stroke:#5294e2;stroke-width:0.99999994;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
+       style="display:inline;opacity:1;fill:url(#linearGradient4139);fill-opacity:1;stroke:url(#selected_bg_color);stroke-width:0.99999994;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1"
        id="rect4160"
        width="31"
        height="31.000017"