diff --git a/web/src/features/psuInsights/components/map/psuFeatureStylers.test.ts b/web/src/features/psuInsights/components/map/psuFeatureStylers.test.ts
index b8c782833..f5d13d3ad 100644
--- a/web/src/features/psuInsights/components/map/psuFeatureStylers.test.ts
+++ b/web/src/features/psuInsights/components/map/psuFeatureStylers.test.ts
@@ -1,4 +1,4 @@
-import { setTransparency } from '@/features/psuInsights/components/map/psuFeatureStylers'
+import { getColorForRasterValue, setTransparency } from '@/features/psuInsights/components/map/psuFeatureStylers'
 
 describe('setTransparency', () => {
   it('should return an rgba value from rgb with correct alpha value', () => {
@@ -17,4 +17,17 @@ describe('setTransparency', () => {
     const incompleteColor = 'rgb(1, 2)'
     expect(() => setTransparency(incompleteColor, 0.5)).toThrow(Error)
   })
+
+  it('should return a completely transparent colour if no colour is provided as input', () => {
+    const rgba = setTransparency(undefined, 0.5)
+    expect(rgba).toBe('rgba(0, 0, 0, 0)')
+  })
+})
+
+describe('getColorForRasterValue', () => {
+  it('should get the correct colour for the specified raster value', () => {
+    const rasterValue = 1
+    const colour = getColorForRasterValue(rasterValue)
+    expect(colour).toBe('rgb(209, 255, 115)')
+  })
 })
diff --git a/web/src/features/psuInsights/components/map/psuFeatureStylers.ts b/web/src/features/psuInsights/components/map/psuFeatureStylers.ts
index b38fa2e43..26571e0ff 100644
--- a/web/src/features/psuInsights/components/map/psuFeatureStylers.ts
+++ b/web/src/features/psuInsights/components/map/psuFeatureStylers.ts
@@ -22,9 +22,9 @@ const rasterValueToFuelTypeCode = new Map([
   [14, 'M-1/M-2']
 ])
 
-const getColorForRasterValue = (rasterValue: number): string => {
+export const getColorForRasterValue = (rasterValue: number): string | undefined => {
   const fuelTypeCode = rasterValueToFuelTypeCode.get(rasterValue)
-  return fuelTypeCode ? colorByFuelTypeCode.get(fuelTypeCode) : null
+  return fuelTypeCode ? colorByFuelTypeCode.get(fuelTypeCode) : undefined
 }
 
 /**
@@ -33,7 +33,7 @@ const getColorForRasterValue = (rasterValue: number): string => {
  * @param alpha number value between 0 and 1
  * @returns rgba value with alpha set ex. rgba(1, 2, 3, 0.5)
  */
-export const setTransparency = (color: string, alpha: number): string => {
+export const setTransparency = (color: string | undefined, alpha: number): string => {
   if (!color) return 'rgba(0, 0, 0, 0)'
   const rgbMatch = color.match(/\d+/g)
   if (!rgbMatch || rgbMatch.length < 3) {