fix: usage page make it work with graphColorMapping flag (#4195)

Author: ChitlangeSahas

src/visualization/utils/colorMappingUtils.ts

@@ -159,7 +159,14 @@ export const generateSeriesToColorHex = (
   const cgMap = {...columnGroupMap}
   cgMap.mappings.forEach((graphLine, colorIndex) => {
     const id = getSeriesId(graphLine, columnGroupMap.columnKeys)
-    const colors = properties.colors ?? DEFAULT_LINE_COLORS
+    let colors
+    if (Array.isArray(properties.colors) && properties.colors.length) {
+      // takes care of when properties.colors is NOT undefined, and NOT an empty array
+      colors = properties.colors
+    } else {
+      // when array is undefined or array IS empty.
+      colors = DEFAULT_LINE_COLORS
+    }
     const colorsHexArray = colors.map(value => value.hex)
     const fillScale = getNominalColorScale(columnGroupMap, colorsHexArray)
     seriesToColorHex[id] = fillScale(colorIndex)