I crossed Aztec gold Daylily with Happy returns Daylily, and I am wondering what their seedlings will look like, when they bloom

I'm guessing you're talking about Plumeria. Is there a question about this cross?

Pretty certain they would be yellow but as far as bloom size and shape, it could resemble either parent.

They should all have yellow flowers, although the actual shades?/tints? of yellow may differ. Any seedlings that have reddish or purplish (etc.) colours were produced by natural insect pollinations.
Scape height will vary from that of 'Happy Returns' registered as 18" to that of 'Aztec Gold' registered as 36". The average scape height of all their seedlings would be about 27" (if the registered heights of the parents are those in your growing conditions).
The flower size of 'Aztec Gold' was not indicated when it was registered. The flower size of the seedlings would be expected to vary from that of 'Happy Returns' at 3.1" to whatever size 'Aztec Gold' flowers are in your growing conditions with many of the seedlings having flower sizes near the average of the two parents.

Brightstar3 said:I crossed Aztec gold Daylily with Happy returns Daylily, and I am wondering what their seedlings will look like, when they bloom.

I'm fascinated by the idea of this cross! (I don't think your picture "lightboxes" pasted in correctly, just FYI.)

I have 'Happy Returns' again finally. It stayed in the ground at the last house I rented, and I don't think I dug any up when I went back for "just a few fans" (with that landlord's permission, of course). I bought replacement HRs this past summer (on Lowe's plant clearance, as is my wont).

Aztec Gold was one I loved and lost with my house in a foreclosure situation back toward the beginning of the last financial crisis. It had such an interesting color and flower shape!

I'm intrigued by what the cross seedlings will be like. I look forward to seeing your results!