I have been successful in saving tubes from 12 plants for 3 sraight years. Only problem is they are all same color..........where can I buy white or yellow seeds??

Hazzards seeds have several different Four-O-Clock strains, but in mixed colors.

https://www.hazzardsgreenhouse...

Burpees also offer Four-O-Clock mixed colors

https://www.burpee.com/flowers...

ZM (not associated with any product or vendor mentioned or linked)

There is Marbles Yellow and White sold by Burpee and Swallowtail but it is out of stock now. Burpee is more expensive. Swallowtail also has a very pretty white called Fairy Trumpets. I never grew either but the pictures are nice.
https://www.swallowtailgardens...
Everwilde sells white, yellow and a few others.
everwilde.com/Four%20O'Clock-Garden-Wildflower-Seeds.html
I have bought from these companies before but if you search four o'clocks by flower color, you will get more options.