Dilute means to reduce the colour of the bird through selective breeding. If the ground colour is green you'll end up with a yellow masked lb and if the ground is blue then you'll end up with a white masked lb. Two white masked lb's can have albino babies and two yellow's can have lutinos.
If both parents have a ground colour of green then the bird will have a yellow body with an orange face and red eyes. If the parents ground is blue then this will result in albinos. An albino is a creature with no colour pigment at all in the body leaving them with white bodies. The only colour in an Albino is their red eyes.
To get a slate-masked lb you need a blue-mask with two dark factors. The overall body colour of this bird is very dark with a white bib and neckline.