[Lens] Add ability to set colors for y-axis series (#70311) (#70719)

Author: flash1293

x-pack/plugins/lens/public/xy_visualization/__snapshots__/xy_expression.test.tsx.snap

@@ -5,7 +5,7 @@
  */
 
 import { EuiIconType } from '@elastic/eui/src/components/icon/icon';
-import { SeriesType, visualizationTypes } from './types';
+import { SeriesType, visualizationTypes, LayerConfig, YConfig } from './types';
 
 export function isHorizontalSeries(seriesType: SeriesType) {
   return seriesType === 'bar_horizontal' || seriesType === 'bar_horizontal_stacked';
@@ -24,3 +24,12 @@ export function getIconForSeries(type: SeriesType): EuiIconType {
 
   return (definition.icon as EuiIconType) || 'empty';
 }
+
+export const getSeriesColor = (layer: LayerConfig, accessor: string) => {
+  if (layer.splitAccessor) {
+    return null;
+  }
+  return (
+    layer?.yConfig?.find((yConfig: YConfig) => yConfig.forAccessor === accessor)?.color || null
+  );
+};

x-pack/plugins/lens/public/xy_visualization/state_helpers.ts

@@ -188,7 +188,8 @@ export const buildExpression = (
                               function: 'lens_xy_yConfig',
                               arguments: {
                                 forAccessor: [yConfig.forAccessor],
-                                axisMode: [yConfig.axisMode],
+                                axisMode: yConfig.axisMode ? [yConfig.axisMode] : [],
+                                color: yConfig.color ? [yConfig.color] : [],
                               },
                             },
                           ],

x-pack/plugins/lens/public/xy_visualization/to_expression.ts

@@ -100,6 +100,10 @@ export const yAxisConfig: ExpressionFunctionDefinition<
       options: ['auto', 'left', 'right'],
       help: 'The axis mode of the metric',
     },
+    color: {
+      types: ['string'],
+      help: 'The color of the series',
+    },
   },
   fn: function fn(input: unknown, args: YConfig) {
     return {
@@ -195,6 +199,7 @@ export type YAxisMode = 'auto' | 'left' | 'right';
 export interface YConfig {
   forAccessor: string;
   axisMode?: YAxisMode;
+  color?: string;
 }
 
 export interface LayerConfig {