fix: add comment

Author: arjunlalb

projects/observability/src/shared/components/cartesian/chart.ts

@@ -23,6 +23,7 @@ export interface Series<TInterval> {
   units?: string;
   summary?: Summary;
   color: string;
+  // Override the default color string using a method that takes data point as input
   getColor?(datum?: TInterval): string;
   name: string;
   symbol?: SeriesSymbol;