Solder mask is not insulation for high voltage. The specifically states that for creepage calculations, solder mask provides only marginal improvement in pollution degree. Never assume green paint replaces air gap.
Differentiating design rules based on the end-use environment (Class 1, Class 2, and Class 3). Understanding IPC Product Classes Ipc-2221 Pcb Design Pdf
In the , you will find logarithmic charts showing: Solder mask is not insulation for high voltage