The inheritance of color in flowers is a large field, especially, as it varies in different species. Color can be either dominant, recessive, or additive in nature, in different species, and in some plant species it can be a combination of these factors. Also some plants have two or more different genetic defects to make them white or non-colored. Orchids form at least two types of whites which when selfed give all white seedlings, but when crossed with each other, give all colored ones. Clivia similarly have two types of yellow forms which when crossed give all reds or oranges.

As to Four-O-Clocks (Mirabilis multiflora), it is interesting that Mendel did experiments with this plant along with his better known work with garden peas.
Four-O-Clocks show an additive effect with red color for instance. If a red is crossed with a white, all seedlings are pink. Crossing these pinks with themselves, gives white, pink, and red in ratio 1:2:1. For some of the other colors, yellow is dominant over white always. Yellow crossed white gives all yellow. Selfing these gives white and yellow in ratio 1:3. Color patterns like stripes are other genes seperate from color. Try to do a google search probably on flower color genetics as a broad topic. Sticking just to Four-O-Clocks will likely give too few results, and most of the general stuff applies in some way like the expected ratios and such,

Hope this helps.

George

You will have to look at information for each kind of plant in question.

Some basic starting books might be (Im more familar with veggies) those by Kalloo. Otherwise you should look for specific books or journal articles.

K

Please send me information as this is important to me.

The genetics of dahlia colors have been studied for many years. Here is a link to an article: http://members.shaw.ca/hydahlia/FEDworkshop.html

If you want red streaks, try crossing your yellow four o'clock with a white.

The American Naturalist 56: 64-79 (1922)
The Nature of Bud Variations as Indicated by Their Mode of Inheritance (excerpt)
Professor R. A. Emerson, Cornell University

What appears to be a similar result in Mirabilis has been reported by Correns (1903, 1904). Crosses of a supposedly pure white race with several self-colored pink, yellow, and pale yellow races resulted in every case in plants with strongly red-striped flowers and with numerous self-red flowers or even whole branches of such flowers. Intercrosses of the pink and yellow races gave only self-colored progeny, from which fact it was concluded that the white-flowered race carried a latent factor for striping. It was later discovered that about three per cent. of the flowers of the white race showed minute flecks of red. It was evidently an extremely light, variegated race, rarely if ever throwing somatic self-color mutations when the variegation gene was duplex (homozygous material) but producing such mutations with considerable frequency when that gene was simplex (heterozygous material). Correns concluded that red variegation of Mirabilis flowers is a character that, with self-fertilization or inbreeding, remains almost completely latent, but which, through the entrance of foreign germ plasms, is brought to full expression.