Sorry,I meant to get back to you earlier but wasn't sure of the best advice to give.I live in SE England and have 50 different JMs so you'd think the garden would be a blaze of colour in autumn.The truth is it isn't.Autumn colours are very variable anyway but we rarely seem to get the right conditions for a good display.Invariably I just get a hint of what might be as the last few leaves turn lovely colours.
Having said that this shouldn't put you off,choosing a very sheltered position will help greatly as will autumn sunshine(our downfall ha)
If you want bright red,'Osakazuki' is renouned for this,having a slight orange hue it really can glow and after 3years mine is finally showing this trait.It will be plain green the rest of the year though.You can also take your pick from the many red cultivars out there,they nearly all have red autumn colours however 'Bloodgood' here has never shone for me despite being one of the few still with leaves on at the peak time.The rest of the year they're all dark purple here,despite claims none really shine above others.A constantly reliable performer for me has been 'Sango Kaku',again plain green the rest of year,it always produces good orange then yellow autumn colours,and the younger stems are bright red.
Sorry I can't be of more help but autumn colours are simply not guaranteed here.