A single cream gene in a black horse may not be apparent. Genetically this is just is not true, a chestnut horse can not pass on the palomino gene, as they do not carry the gene. The cream gene is dominant to chestnut, therefore if a base chestnut horse carries one cream gene, the horse will always be a palomino. Since every chestnut horse has 2 chestnut genes, if you breed 2 chestnut horses - you will always get a chestnut baby. The foal could possibly have white on it or even be an Overo - but its base color will always be chestnut and it will have non black points.
Palomino horses carry one chestnut gene and one cream gene.
A palomino sire and a field full of palomino mares will not breed true. In this case, you should get about half palominos, with the remainder being chestnut and cremellos. Cremello horses carry no chestnut genes and two cream genes. They are considered a double dilute chestnut. Since cremello horses are homozygous dilute, all offspring of a cremello will carry the dilute or cream gene.