add high contrast theme

frontend/src/app/components/pool/pool.component.scss

@@ -190,7 +190,7 @@ div.scrollable {
 }
 
 .data-title {
-  color: #4a68b9;
+  color: var(--title-fg);
   font-size: 14px;
 }
 

frontend/src/app/components/pool/pool.component.ts

@@ -175,7 +175,7 @@ export class PoolComponent implements OnInit {
         borderRadius: 4,
         shadowColor: 'rgba(0, 0, 0, 0.5)',
         textStyle: {
-          color: '#b1b1b1',
+          color: 'var(--tooltip-grey)',
           align: 'left',
         },
         borderColor: '#000',