Mind officially blown. Wish someone had explained this so clearly to me about 5 years ago! Ha ha haaa!!!There's two main ways to get solid white chicken. The sneaky, recessive one that pops up is called recessive white. White silkies are recessive white.. so are the white legbars as Pyxis mentioned.
Recessive white is a single gene and it does a good job at making chickens solid white, it does not matter what color or pattern genes the bird has- black, red, gold, barred etc. they are all turned solid white.
The other way to make solid white chickens is with Dominant White. It's great at 'converting' black pigments to white.. but cannot convert red/gold pigments to white- leaving the red/gold areas mostly unaffected. Examples of this are Gold laced vs Buff laced, Dark vs White laced red Cornish... Red duckwing vs Pyle/ In all of these the only difference is the presence of DW- it changed the black areas to white, leaving the red/gold areas.
This leads to a neat trick to making a solid white bird using DW- putting it on solid black chickens- presto, solid white chickens. All it did was convert the black into white. White Leghorns are a classic example of this.
To repeat a little bit, in hopes of making it clearer.... let's say pick a breed and color example- Buff Orpington. Recessive white would make the buff orp solid white. Dominant white would.... have either zero effect, it would still look the same as any other buff orpington or possibly a shade lighter- a little more blonde perhaps.
Okay how about a black Orpington? Both recessive and dominant white would turn it totally white no problemo.
Been avoiding white all this time because I thought all white worked like recessive white. Did not understand there were two different genes. DOH!