First get the crank measured to make sure its journals are round, or if it needs a regrind ect.
The shells that are colour coded are the crank mains, there are three sizes of journal; standard, -.25mm and -.5mm, Within each of these three sizes there are a further 3 sizes which are denoted by dots on the crank counter weights (yellow, green or white). These colour coded bearings can only be found at main dealers and are quite expensive. Non genuine ones can be had for about £60-70 but they only come in the three main sizes they are quality items though (Federal Mogul Glyco).
The difference between the coloured dot grade sizes is literaly a gnats cock or .06mm, 6/100th of a mm.
I have built engines with both types without issues, but it is BMWs over-engineering style to have 3 size grades within another, I have had an original engine presumably with the dot bearings in run to well over 300,000 miles and still be within tolerance, it had FSH to 260,000 though. The choice is yours the BMW ones are twice as much as good aftermarket ones.
The big end ones are not dot coded, so just three sizes as the main journals instead the red and blue refurs to it being for the rod or the cap
HTH Maggs
