When we list equations it's Father+Mother=Child
Human+Darsite means a man from Earth and a woman from Darse
Darsite+Human means a man from Darse and a woman from Earth

For Darsites, the eyes are the important feature for their survival. It's the dominant gene. The next generation will have the bottom liner and have a greater chance of having a pale eye colour.

Human

Human males have a dominant gene to determine gender. Human females have the inferior gene to determine gender. This means that if a human male fathers a child, it has a higher chance of being born male. If a human female mothers a child, it has the same gender ratios that Darse has.
Human+Darsite=2 boys for every girl, sometimes 3 boys for every girl. Black lips, bottom eye liner and pale eyes
The next generation+Darsite=1 or 2 boys for every girl with black lips, top & bottom eye liner and pale eyes.
The third generation+Darsite=1 boy for every girl with fully Darsite genetics

Human+the next generation=2 boys for every girl with black lips, no eye liner and darker eyes
Human+the third generation=1 boy for every girl with dark red lips and darker eyes, possibly even brown.
Even when you have a 2nd generation+2nd generation, the gender ratios hold up. However the bottom eye liner stays around longer and the eyes take longer to become dark shades (if they are on Earth) or revert back to pale colours (if they live on Darse). The lips can also change colour either way depending on which planet they live on.

Darsite+human=either gender with black lips, bottom eye liner and pale eyes
Darsite+the next generation=black lips, top & bottom eye liner and pale eyes. In other words, fully Darsite again.

Glacian

Darsites have different strong genes. The Glacian blue hair will remain the dominant gene so the child will be considered Glacian. However, due to the similarities in colour palette between the species, the offspring will have more traits in common with the other parent.

Given the alliance between these species, they have produced offspring for generations so the effects are well-known. When the male birth rate began declining on Glace, it began declining with these mixed offspring too. Hope for the future would not come from this direction. However, pairings are still popular for those looking for a compatible partner.

Darsite+Glacian=Girl with Glacier blue hair and pale eyes with bottom liner blue and black lips

Neanderthal

The Neanderthal dominant genes are hair colour and noses. Lips are strong genes in both species, although they both have similar shapes.

Neanderthal men like having sex with different species but marry Neanderthal women. Neanderthal women insist on marriage before sex. They don't think many species want to have sex with them, and they are right.

Neanderthal+Darsite=either gender with black lips, blue liner under the eyes and pale eye colour. Hair will be darker.
Neanderthal+the next generation=black lips, no eye liner, pale eye colour. Hair will be black now that the Darsite eyes are gone, the other chromosomes have a chance of changing.
Neanderthal+the third generation=dark red lips, darker eye colour, black hair, broad shoulders, shorter height
Neanderthal+the fourth generation=red lips, brown eye colour, black hair, slightly prominent brow, broad shoulders, stocky stature

Darsite+Neanderthal=black lips, blue liner under the eyes and pale eye colour. Hair will be darker
The next generation+Neanderthal=black lips, no eye liner and darker eyes. Hair will be black. Now that the Darsite eyes are gone, the other chromosomes have a change of changing.
The third generation+Neanderthal=dark red lips, darker eye colour, black hair, shorter height
The fourth generation+Neanderthal=red lips, brown eye colour, black hair, shorter height, broad shoulders
The fifth generation+Neanderthal=Neanderthal lips, eyes & hair. Stocky build with broad shoulders. It is in this generation that the brow begins to become prominent because of the continual breeding with Neanderthal Females whose brows are less prominent than male brows.

When you have a 2nd generation+2nd generation, the blue liner under the eyes stays a bit longer as do the iris and lip colours. These colours could change slowly depending on which planet they live on. The hair colour continues to get darker and darker until it is black after a few generations.

Fontian

For Fontians, the hair colour is the dominant gene.

Darsite+Fontian=either gender with black lips, blue liner under the eyes and pale eye colour. Hair will be platinum blond
Darsite+the next generation=paler eye colour, blond hair
Darsite+the third generation=blond highlights to the mother's hair colour

The next generation+Darsite=paler eye colour, blond highlights to the mother's hair colour
The third generation+Darsite=blond sheen to mother's hair colour