It´s worth noting that when CAU mention toe colour as a good separating feature between March and Reed, he actually is refering to claws, not toe.
No problem . I know that the claw colour is an even better feature, but the leg colour is sometimes also useful. Svensson states that it is useless only for adult birds. Nevertheless, the soles on Reed Warblers are typically yellow, I don't think anyone wants to contradict this.