[Mystery colour streaks - WILL PAY FOR SOLUTION]

Hi, I am desparate and willing to pay anyone that can help solve my printer problem for me.

 

PROBLEM:
Random and slightly diagonal lines/streaks across my PLA prints.
Problem only started recently.
Layers are about 1-2seconds long

 

SOLUTIONS TRIED:
Rails - lubricated
Material - swapped with fresh reel
Speed - various
Extrusion - layers all look uniform and accurately laid, only colouring seems affected
Temp - not enough time for temperature to fluctuate so consistently within or between layers
Something loose - layers all look uniform and accurately laid
Stl file or slicer - printed previously without issue

It is only a problem with these parts, because they form part of a desklamp and have light shining through them.

 

Thanks :)