We have a new foreign employee and she said:
"Ich habe keine blasse Ahnung."
We thought it was a mix of
leiseste Ahnung and was done because she is foreign. But she said it was something she looked up. So we looked it up in PONS and there it is.
Now we are wondering is this really used by native speakers and maybe in which region of Germany it might be common. Because we never heard of it here (Ruhr-area, Lower-Rhine-area)