The Honeywell RU6500 Series is a full facepiece respirator manufactured by Honeywell.

There are no off the shelf tint options for this respirator. b4412c has tinted one and traced the cut out tint before applying it. The original scan and an svg traced from it can be found here. In theory it should be possible to print out the trace, verify it is to scale, and use it as a template to cut tint. b4412c has also found success using the trace file to 3d print mesh-like inserts that cover the inside of the lens and can be customized. Bring the trace svg into the slicer of your choice and scale it to 97.5% with a thickness equal to two or three layers. Set top and bottom surfaces to 0 and infill density to a high number. Adjust infill pattern and density to taste.