yes

and what were the results?

depends on the nature of the "white"

most whites are really variants of yellows. so they segregate as with a yellow.

The hybrid result of any are red fruits (or in some exceptions brown if skin of one is yellow and both parents contained the green fleshed gene).

The later generation offspring are likely to produce a mix of black, red, (pink or purple if one parent had clear skin), brown, yellow, green and white if large enough numbers are grown out.

If you want to kill the flavor cross to a white (or Green Doctor's)

-blacks are red fleshed with the green fleshed gene combined
-whites are different expressions of yellows (possible allelic variant/clear skin) and sometimes the green fleshed gene

There are exceptions of other genes that make "white" but these aren't in circulation.

In a black x yellow I have had a orange type called 'apricot' show up.

thank you for sharing that, it's all very fascinating. the apricot sounds the nicest

Thanks for your responses! I don't want to kill the flavor. I really like the taste of the black ones, but they are so small I have to eat them one at a time and contemplate the taste. I have only three of the 'Italian ice' so far and I'm waiting to try them (I'm ADD, so it may take a while for me to find the perfect situation).
If I do a cross, it will be with tomatoes that are large enough to actually experience.
When you refer to green or red flesh, are you referring to the meat of the tomato or the peel or both?

flesh would be the "meat"

skin would be the peel

flesh______peel_____color
red + clear = pink
red + yellow = red
red/green + clear = purple
red/green + yellow = brown
yellow + clear = light yellow/white
yellow + yellow = yellow
tangerine + clear = orange
tangerine + yellow = yellow gold

there are also color differences in the gel surround the seed but they dont really influence the color of the outside

Thanks for taking the time to spell things out for me! Where would P20's fit into this chart? They look like they might be "off the chart".

Is there any color difference between green flesh/clear skin and green flesh/yellow skin?

And what about bi-colors?

Green flesh clear skin would be like Green Giant or Grub's Mysrey Green, green flesh yellow skin would be like Cherokee Green or Cherokee Green Grape.

Bi-color is a whole 'nother story. There isn't as much documented about bi-colors yet. I get the most bi-colors from crosses involving greens & yellows, though blacks can contribute too.

P20 lines potentially have 3 different genes that all have the potential to express anthocyanin (purple pigment) in all different parts of the plant (not just fruit) when environmental conditions are right. In fruit that tends to be just under the skin and only in a few cell layers of the flesh which light is able to penetrate.

The only color difference between green flesh/clear skin and green flesh/yellow skin is that the later matures with an amber cast. It can be difficult to tell when a clear skinned green is ripe. Almost have to go by touch although there is a sublte change to a dull whitish green one can notice with experience. Green Giant is an example of a clear skinned green.

The trait of being bicolor is a recessive gene called "ry". Not a lot of work has been published on it's inheritance.

However from what I have seen with a few crosses ry may be influenced by what are called alleles or modifier genes. In segregating bicolor lines I have observed a continuum of results that I thought at first might be related to environmental expression or fruit maturity but as I have grown out those separate lines I find they are indeed expressing their own degree of bicolored percentages. Such as one line may be 80% yellow and 20% red, whereas others maybe 50/50 or more red than yellow.

With one cross I saw an unusual F1 which may indicate there could be a co-dominance or incomplete dominance situation (in short it produced something intermediate to the two parents rather than one dominating - in Mendel's example it was white x red = a pink F1 flower color).

I havent grown them but I have seen other bicolors which might also be modified by developmental genes that regulate where the differences in color are regularly expressed.