Janet's cardigan sweater is white; though yes, it does look blue-ish in some scenes presumably because of the lighting. Also, if you're watching an older print red is usually the first color to fade and that can have an effect on how the colors look - especially white. It has raglan sleeves (diagonal seams from the armpit to neck instead of a shoulder seam), rib knit cuffs turned back and a ribbed hem. I counted 8 buttons down the front (2-hole). I think they're clear? The sweater's hem is just above her wrists.
It's a simple enough design that you can usually find at a Thrift store or even on eBay with enough perseverance.
