fix(colors): blend method return type should be same as input (#6107)

docs/src/pages/quasar-utils/color-utils.md

@@ -60,9 +60,10 @@ Returns a value between 0 and 255. A value of < 128 would be considered a dark c
 
 Calculates the [blend](https://www.w3.org/TR/compositing-1/#simplealphacompositing) of two colors.
 
-Accepts a HEX/A String, a RGB/A String or a RGB/A Object as `fgColor`/`bgColor`.
+Accepts a HEX/A String or a RGB/A Object as `fgColor`/`bgColor`.
 If the alpha channel of the `fgColor` is completely opaque, then the result will be the `fgColor`.
 If the alpha channel of the `bgColor` is completely opaque, then the resulting blended color will also be opaque.
+Returns the same type as input for fgColor.
 
 ### updateAlpha (color, offset)
 

ui/src/utils/colors.js

@@ -252,7 +252,10 @@ export function blend (fgColor, bgColor) {
     g = Math.round(((g1 * a1 + g2 * a2 * (1 - a1)) / a) * 255),
     b = Math.round(((b1 * a1 + b2 * a2 * (1 - a1)) / a) * 255)
 
-  return rgbToHex({ r, g, b, a: Math.round(a * 100) })
+  const ret = { r, g, b, a: Math.round(a * 100) }
+  return typeof fgColor === 'string'
+    ? rgbToHex(ret)
+    : ret
 }
 
 export function changeAlpha (color, offset) {