Adeniums do not come true from seed. Pink is the most prevalent color. With all the hybridizing that has been done over many years, the likelyhood is greater to receive something close to pod/pollen parents.
The likelyhood of receiving a seedling which produces a yellow or dark purple from Pink pod or pollen parents is probably non existent.
For the best percentages, it is worth purchasing from sellers of good hybridizing practices and proven results.
Some will say that if the color of the seedlings skin is green, then good possibilities of a white bloom and if reddish, then a darker color bloom.
This all becomes quite washed out when we factor in the number of lighter colors and then the dark colors.
I find it easier to not assume or hope for anything other than good growth and for it to bloom. If in fact it is something different or alike, this is good.
Rick