Electrolytic rust removal
If your anode/cathode are from copper, then the blue chemical in the solution is copper chloride (CuCl2).  Copper chloride can be toxic. So you should have safety equipment. 

As for rust removal in general, I'd recommend you to use Citric acid (Squeezing lemons for the lemon juice isn't efficient since it will contain 5-6% Citric acid - so its better to buy powdered Citric acid from a store).