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.
