Allow Stat panel to color one field based on another field’s value (e.g., show Current, color by DeviationPercent)

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: When visualizing service metrics, it’s often necessary to highlight abnormal behavior by comparing current values to historical baselines or calculated deviations. Currently, the Stat panel in Grafana can only color a value based on its own field, not on another field’s value that exists in the same query result. This makes it impossible to, for example, display the Current total of connections but color it based on the DeviationPercent from a baseline - a very common need for overview dashboards. **What would you like to be added**: An option in the Stat panel’s color mode settings to choose which field should be used for color evaluation. For example: > Color by field value: `[Dropdown → select another field]` > > Display field → Current > Color source field → DeviationPercent This would allow users to keep their main metric visible while still reflecting the deviation or trend via color thresholds. It should work with multi-field queries and support transformations (e.g., “join by field”, “calculate field”). **Who is this feature for?** This feature would help anyone building overview dashboards or service health panels, where the main metric (e.g. total connections, load, or latency) is displayed prominently, but its color should reflect a secondary analytic metric like deviation, anomaly score, or forecast error. **Example setup:** - Data source: Zabbix plugin v6.0.3 - Grafana version: 12.2.1 - Fields: - _Current_: current total connections - _DeviationPercent_: calculated as `(1 - Current / 15-min average from 7/14/21/28 days ago) * 100` Expected behavior: → The Stat panel shows the Current value, but its color thresholds are applied based on DeviationPercent.