Go on then I'll bite.

The green bar represents the horses fitness the red bar it's stamina or energy. The two work in an antagonist manner to each other depending on the training you select. So when the horse is rested green will decline and red will increase, when in full training the reverse is true.

Exported horses are exported exactly as they are in game, so if you export an injured game horse you will get an injured league horse, thus for league fitness you want full green. Training notes that say 'raring to go' or 'fit and ready to race' and it is best to keep the red bar as high as possible as when depleted you may find the horse cannot be got back to fitness until the next season. 50-70% red is ok in my experience.

thanks for biting
i didnt know that 2yo's ive exported are low on the red bar

Green is key. Note if the training notes say 'care your over racing this horse' you have had it with him for the season.

At the top of this forum there is a long post called 'rags to riches' you may find it useful.

What schedule do you play?

If a U.K. Combined schedule so jump and flat, the first point you can 'pool' them is when they are 2yo. So save your game say 1st April, mark them too pool, play through to the end of the year then check your transfer window and you should see your horses. Crash your game without saving and then reload to the save point. Un -check them for pool, checking the pool again to be safe as pooling can be glitchy and finish the season normally, you can now play on and you have the horses saved.