Some colors of plumage affect the color of legs and beaks, especially early in life... Splash and White plumage colors both suppress the black pigment which is normally found in silkie skin and other tissue. It can take a while for the black color to show up, and it may be a muted bluish grey when it does.
That said, virtually none of the show silkies in the silkie world are really, truly "pure bred": the original chinese Wushan fowl is a white silkie with a smaller crest and more tapered, upright posture than you see in american show silkies. After bringing these birds to the West, chicken fanciers worked on increasing their crest, making them "fluffier" and rounder, and expanding the color range. You can be pretty sure that any silkie with a vaulted skull has some polish ancestry, and colors like buff and andalusian blue / splash were brought in by crossing with other breeds. By crossing the cross-breeds back to a line of silkies, keeping the chicks with the desired coloring who still have a lot of silkie traits, and repeating the process over and over, you can increase the concentration of silkie to the point where the other breed's traits aren't noticable.
Here's an example of how you could try to get a lavender silkie by crossing with lavender d'Uccle bantam: the lavender color comes from a combination of extended black gene (to get a black background) plus the lavender gene (to dilute the black to a pale grey color).
To make it easier we will start with a black silkie
D'Uccle bantams already have beards, feathered legs and small stature, which are traits we want to keep.
5 toes, extended black color, rose comb, pea comb, and leg feathering are dominant genes. Any bird which carries these genes will show it.
Lavender, crests, beards, and silkie feathers are recessive genes. A bird must inherit 2 copies of the gene (one from each parent) or else it doesn't show in the bird's appearance.
The fibromelanosis gene, which gives silkies their unique dark skin, is partially dominant; if a chicken has one of the gene, they'll probably be at least grey. Having 2 of the gene gives a chicken black skin (although diluters like the lavender gene will lighten the color).
1st generation: 100% black bearded silkie X 100% lavender d'Uccle bantam = 50% silkie F1 crosses
All the F1 generation will be black and bearded, with non-silkie feathers, 5 toes, and feathered legs. The lavender gene is recessive, and only one parent had it, so it is hiding right now.
2nd generation: F1 X F1 = F2 crosses ( <100% silkie, averaging about 50% silkie genes )
Some of these crosses will have the recessive silkie feathering; about 1/4 of them will have lavender feathers; many will have 5 toes; most will have grey or black legs; all will have leg feathering and beards; about 1/4 will have crests .
For this example, the breeder keeps only those birds who are lavender in color.
3rd generation: lavender F2 X 100% black bearded silkie = at least 50% silkie, averaging about 75% silkie genes.
Once again, all the offspring are black, but all of them carry the lavender gene.
4th generation: 3rd generation X 3rd generation ( averaging about 75% silkie genes ).
At this stage, the breeder has another opportunity to pick out lavender birds, especially any who show the special silkie recessive traits (crest, dark skin, and silkie feathers) .
5th generation: lavender 4th generation X 100% black bearded silkie = at least 50% silkie, averaging about 87% silkie genes. These offspring are starting to look a lot like black bearded silkies.
6th generation: 5th generation X 5th generation (averaging about 87% silkie genes)
The breeder selects the birds who are lavender colored, and who look the most like silkies in outward appearance.
And so on:
7th generation: lavender 6th generation X 100% black bearded silkie = averaging about 93% silkie genes and looking a heck of a lot like black bearded silkies
8th generation: 7th generation X 7th generation, pick the lavender ones; genetically, about 93% silkie
...
10th generation: genetically, about 96% silkie
...
12th generation: about 98-99% silkie
Stop whenever you are satisfied with the result.
Throughout the process, you should be using a variety of different, unrelated black silkies as parent stock, to give your new lavender line a healthy amount of genetic variety.
Best - exop
