[v10.0.x] Elasticsearch: Fix histogram colors in backend mode (#71447)

Elasticsearch: Fix histogram colors in backend mode (#71442)

elastic: backend-mode: fix histogram colors
(cherry picked from commit fdb8257007)

public/app/plugins/datasource/elasticsearch/datasource.ts

@@ -32,6 +32,7 @@ import {
   Field,
   LogRowContextQueryDirection,
   LogRowContextOptions,
+  FieldType,
 } from '@grafana/data';
 import { BackendSrvRequest, DataSourceWithBackend, getBackendSrv, getDataSourceSrv, config } from '@grafana/runtime';
 import { queryLogsVolume } from 'app/core/logsModel';
@@ -683,7 +684,7 @@ export class ElasticDatasource
       {
         range: request.range,
         targets: request.targets,
-        extractLevel: (dataFrame) => getLogLevelFromKey(dataFrame.name || ''),
+        extractLevel,
       }
     );
   }
@@ -1282,3 +1283,9 @@ function createContextTimeRange(rowTimeEpochMs: number, direction: string, inter
     }
   }
 }
+
+function extractLevel(dataFrame: DataFrame): LogLevel {
+  const valueField = dataFrame.fields.find((f) => f.type === FieldType.number);
+  const name = valueField?.labels?.['level'] ?? '';
+  return getLogLevelFromKey(name);
+}