^^^ yes, you would have to sand away the green tint if you want a white gauge cluster
Also, as for going blue, you don't actually need to sand away the green tint because the two colors are close in the color spectrum. If you go back 2-3 pages, you can see a picture of my gauge cluster. I simply used blue LEDs that were 3 times the brightness without modifying anything else and the result is quite blue. It does looks slightly teal, but I was fine with it.
Just leave the Odometer bulb stock, or maybe use a white led, because otherwise your needles would become very dim and hard to see.
The whole process took me about 30 min., including the time it took to remove the gauge cluster.