I must confess I haven't yet understood Silver vs Gold, as I keep thinking in terms of Red vs Black. Is it the same thing?
No, gold vs. silver is not the same thing as red vs. black.
Chickens mostly have two pigment colors, black and red.
Those two colors can be arranged on the body by various genes, making various patterns, or making a chicken that is solid black or solid gold.
Black can be modified to other shades (blue, splash, lavender, chocolate, khaki, and the gene called Dominant White turns black into white.)
Gold can be modified to other shades (cream, mahogany, and the gene called Silver turns gold into white.)
The silver/gold gene is located on the Z sex chromosome.
A hen has chromosomes ZW. Because she has only one Z chromosome, she is silver or she is gold, but she never has both genes. She inherits her W chromosome from her mother, and passes it on to her daughters. She inherits her Z chromsome from her father, and she passes it on to her sons. So a hen can only inherit silver or gold from her father, and can only give it to her sons. Silver or gold never passes from a hen to her daughter.
A rooster has ZZ sex chromosomes. So he can be pure for silver, pure for gold, or have one of each. Silver is dominant, so it is the one that shows when he has both. But when he has both genes, the silver color is more likely to be yellowish (like the color on your rooster), and when he is pure for silver the color is more likely to be a nice clean white. A rooster inherits silver or gold from both parents, and passes one or the other of his Z chromomes (with the silver or gold gene) to every chick he sires.
Is the Blonde wash on Colonel Custard here because of Gold?
It might be, but I'm not entirely sure. There are several things that can cause feathers to yellow like that.
When you talk about his "brothers," do they all have exactly the same parents? If yes, then it is quite likely that he does have both silver and gold.
If his mother or his father was gold, then he would have to have the gold gene. But if his mother was silver, and his father was silver while carrying gold, then Custard could be carrying gold or could be pure for silver, and you wouldn't know for sure until you see what color chicks he produces. If he sires any gold chicks (sons or daughters), you would know for sure that he has the gold gene.
He has a straight black barred brother, and this is one of his many "Red" brothers, with a black chest...
(some of the reds have pale chests with slightly lighter saddles, but less distinct barring).
The differences between the black brothers and the red ones are caused by some of the genes that control where the red vs. black go on the chicken. The black ones also have silver or gold or both, but you can't see which because of them having black all over (no place to show the gold or silver).
The white barring is caused by yet another gene, that puts white bars on the chicken no matter what other color genes it has. Of course, white bars can make it harder to see whether a chicken actually has some silver, because barring and silver both put white on the feathers.