Red fleshed indications -apples

As most know my thing so far is searching out seedling apples growing wild that are special enough to try growing as new apples. At the same time I am also growing apple seedlings for rootstock. With the wild apples they are already fruiting so I can sample the fruit ( most times) . With the seedlings I would like to grow out any thing that might produce red fleshed fruit just to see. I know many here already grow red fleshed varieties and others are also crossing and growing out seedlings from red fleshed varieties. So how strongly/ consistently do red flesh apples show indications (such as red wood or red leaves) of being red fleshed without having to have fruit to sample. And are there any other indications they might show without having fruit to sample.