refactor: finished converting sass colors in _session_signin.scss

stylesheets/_session.scss

@@ -919,7 +919,7 @@ input {
     }
 
     &-disabled {
-      border: 1px solid $session-color-dark-grey !important;
+      border: 1px solid var(--color-darker-gray-color) !important;
     }
   }
 }

stylesheets/_session_constants.scss

@@ -111,8 +111,6 @@ $session-shade-15: #5b6c72;
 $session-shade-16: #979797;
 $session-shade-18: #141414;
 
-$session-color-dark-grey: #353535;
-
 // Semantic Colors
 $session-color-info: $session-shade-11;
 $session-color-success: #35d388;

stylesheets/_session_signin.scss

@@ -2,7 +2,7 @@
   &-fullscreen {
     width: 100%;
     height: 100%;
-    background-color: white;
+    background-color: var(--color-white-color);
   }
   &-content {
     .session-button.brand-outline.brand.green:hover {
@@ -197,7 +197,7 @@
     justify-content: center;
     padding: 20px;
     border-radius: 13px;
-    border: 1px solid subtle(#353535);
+    border: 1px solid subtle(var(--color-darker-gray-color));
     margin-bottom: 20px;
 
     textarea {

ts/themes/SessionTheme.tsx

@@ -48,7 +48,7 @@ const darkColorClickableHovered = '#414347';
 const darkColorSessionBorder = `1px solid ${borderDarkThemeColor}`;
 const darkColorSessionBorderColor = borderDarkThemeColor;
 const darkColorRecoveryPhraseBannerBg = '#1f1f1f';
-const darkColorPillDivider = '#353535';
+const darkColorPillDivider = 'var(--color-darker-gray-color)';
 const darkColorLastSeenIndicator = accentDarkTheme;
 const darkColorQuoteBottomBarBg = '#404040';
 const darkColorCellBackground = '#1b1b1b';