My experience with main bearings is very limited, I have done some rod bearings on a few engines but on those they just say to use plastigauge to verify clearance and if you need an oversized bearing you install as a set. I've checked a few mains "while I was in there" during some jobs but never found a reason to replace them, they always check out fine with plastigauge.
How I interpret it though is that the baseline value is the marking on the crank, per TIS:
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The crankshaft is marked with yellow, green or white paint according to the tolerance of the main journal.
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TIS gives you a table on the bearings and their sizes, you'd want to be using the "standard" size unless you have a reason not to.
ie. If cyl 2 is marked green, and cyl 4 marked yellow, you'd use:
cyl 2 Bearing shell green 70.00MM (0)
cyl 4 Bearing shell yellow 70.00MM (0)
If you needed .50 over then you'd use:
cyl 2 Bearing shell green 69.50MM (+0.50)
cyl 4 Bearing shell yellow 69.50MM (+0.50)
This gets a little muddy for me because oversized bearings have the material added to the back of the bearing, to account for the mains being line honed for example (if it was line honed .50 you'd use .50 over bearings). But the BMW nomenclature showing sizes getting incrementally smaller (.50 "over" is .50 smaller than the standard 70) makes me think BMW is counting on you grinding and polishing the crank, and do not have anything in their catalogue to account for line honing. Really, they should be considered undersized if this is the case - so 69.50 (-.50) would be more accurate.
But that is somewhat a moot point, I do suspect you'll be fine running standard bearings across the board. If nothing else changed (crank wasn't ground, no line honing was performed) then I don't see why you'd deviate from standard size.
As you noted, TIS has a note that you use all yellow in the crankcase side
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When crankshaft or main bearing shells are being replaced, the classification for the arrangement of the main bearing shells in the crankcase is no longer of significance. Install yellow main bearing shells in crankcase.
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And to install bearings matching the crankshaft marks on the crankshaft side
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Place main bearing shells with same color code as that of crankshaft in main bearing caps.
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I would trust TIS on this and order standard yellow bearings for the main bearing side and standard (matching the indicated colors) on the cap side, verify with plastigauge, and if the plastigauge indicates it's ok on both sides then it should be good to go.