|Dampen a white paper kitchen roll sheet with surgical spirit, and gently try removing the marker. |
A cotton bud/q-tip is also good for this task.
Clean then dry (again using kitchen roll) as you go, as you do not want an excess of cleaner aorund.
Often forgotten is that plastic is not glass, and and can be slightly porous such that some fluids can 'soak' in. A little white vinegar can also help with this.
Please advise back on progress.
Good Luck - Keep us posted.