BLUE BAR SMOKEY. This bird is also a blue bar, but it carries other genetic factor also, smokey and likely sooty. Notice the false checking on the wing shield - that's the sooty factor and also note the smeary or wash-out looking bars, that's smokey. If we could spread the tail, we would also note that the outer two tail feathers are missing the whitish (albescent) strip they normally have. Smokey birds are known by racing homer fanciers as slates. Smokeys often show a lightened beak. Birds which carry sooty sometimes do not show the false checking on the wing until they molt into their adult plumage. Smokey birds often have the bars washed out, so much so on occasion that they can be mistaken for barless birds.
BLUE CHECK. Check is an extremely common mutation in pigeons and may even be more common than bar. The check marking is actually the darkened feather of the wing shield. There are different alleles, or alternatives, in the check series which can be important in breeding some of the Color Pigeons for show, but this bird well illustrates the medium to light checker where the checking and lighter ground color are about even.
T-Pattern checker. This is one of the check alleles, CT, and is characterised by little or no ground color showing through. A bird like this is sometimes called a velvet or blue-tailed black by racing homer fanciers. Note the tail of this bird is still a wild-type tail. The terminal tail bar is visible, so this bird is not carrying spread, which is a totally different mutation and is not part of the pattern series.