factor out some more colours

src/skins/vector/css/matrix-react-sdk/structures/_UserSettings.scss

@@ -58,7 +58,7 @@ limitations under the License.
     clear: both;
     margin-left: 63px;
     text-transform: uppercase;
-    color: #3d3b39;
+    color: $h3-color;
     font-weight: 600;
     font-size: 13px;
     margin-top: 26px;
@@ -166,10 +166,10 @@ limitations under the License.
 {
     display: inline-block;
     border: 0px;
-    border-bottom: 1px solid rgba(151, 151, 151, 0.5);
+    border-bottom: 1px solid $input-underline-color;
     padding: 0px;
     width: 240px;
-    color: rgba(74, 74, 74, 0.9);
+    color: $input-fg-color;
     font-family: 'Open Sans', Helvetica, Arial, Sans-Serif;
     font-size: 16px;
 }

src/skins/vector/css/matrix-react-sdk/structures/login/_Login.scss

@@ -147,7 +147,7 @@ limitations under the License.
 }
 
 .mx_Login_error {
-    color: #ff2020;
+    color: $warning-color;
     font-weight: bold;
     text-align: center;
 /*

src/skins/vector/css/matrix-react-sdk/views/elements/_DirectorySearchBox.scss

@@ -44,7 +44,7 @@ input[type=text].mx_DirectorySearchBox_input:focus {
     padding: 3px;
     padding-left: 10px;
     padding-right: 10px;
-    background-color: #efefef;
+    background-color: $plinth-bg-color;
     border-radius: 3px;
     background-image: url('img/icon-return.svg');
     background-position: 8px 70%;

src/skins/vector/css/matrix-react-sdk/views/elements/_ProgressBar.scss

@@ -16,10 +16,10 @@ limitations under the License.
 
 .mx_ProgressBar {
     height: 5px;
-    border: 1px solid black;
+    border: 1px solid $progressbar-color;
 }
 
 .mx_ProgressBar_fill {
     height: 100%;
-    background-color: #000;
+    background-color: $progressbar-color;
 }

src/skins/vector/css/matrix-react-sdk/views/rooms/_MemberInfo.scss

@@ -61,7 +61,7 @@ limitations under the License.
 
 .mx_MemberInfo h3 {
     text-transform: uppercase;
-    color: #3d3b39;
+    color: $h3-color;
     font-weight: 600;
     font-size: 13px;
     margin-top: 16px;

src/skins/vector/css/matrix-react-sdk/views/rooms/_MemberList.scss

@@ -96,7 +96,7 @@ limitations under the License.
 
 .mx_MemberList_invited h2 {
     text-transform: uppercase;
-    color: #3d3b39;
+    color: $h3-color;
     font-weight: 600;
     font-size: 13px;
     padding-left: 3px;

src/skins/vector/css/matrix-react-sdk/views/rooms/_RoomSettings.scss

@@ -81,7 +81,7 @@ limitations under the License.
 
 .mx_RoomSettings h3 {
     text-transform: uppercase;
-    color: #3d3b39;
+    color: $h3-color;
     font-weight: 600;
     font-size: 13px;
     margin-top: 36px;