Blend references "draw[ing] upon your elven link to the wilderness" but has no requirement nor restriction that you must be an Elf. There is no portion of the spell that you must be an Elf or that non-Elves cannot benefit from it. In fact, as written, even a non-Elf alchemist, druid, magus, psychic, ranger, shaman, sorcerer/wizard, or witch could prepare Blend if taught how by an Elf. In cases where this is not true, the rules say so explicitly
Spell requires a requisite religion or race. If religion, spellcaster must worship the listed deity to utilize the spell. If race, the spell might only target members of the listed race (the spell will say this if it does), but often are just the race's guarded secrets. Members of other races can learn to cast them with GM permission.