What the difference between white and yellow mesh?

Why do we have both white and dyed meshes? All meshes start out white, they dye higher mesh counts yellow because emulsions and stencils are not sensitive to yellow light. When your art work has halftone dots or very fine lines, you need to protect each dot from getting overexposed.
Yellow or dyed mesh blocks all of the blue light spectrum that passes through, which would normally cause the dots or lines to become overexposed making them smaller and difficult or impossible to washout. Dyed meshes take slightly longer to expose, so you may need to adjust your light time. You will notice a difference when you’re able to hold all of your halftones dots.