It seems to me that some colors need の when describing an item, yet others don't.
- 黄色のくつ (Yellow shoes; has の)
- 赤いくつ (Red shoes; no の)
- オレンジ色のくつ (Orange shoes; has の)
- 青いくつ (Blue shoes; no の)
It would seem the kanji for color (色) isn't always mandatory, which I would guess is also related.
Is there some kind of distinction per color, or is it just two ways of saying the same thing?