Sunny, in my understanding, it doesn't really matter if you provide a attested colored photocopy or black and white. All that matters is, your marksheets and degree certificate (or may be just mark sheets alone) must have a official university seal on each of them and they should be place in the envelope and the envelopes openings should be again sealed with university's official seal. That way, visa officers will find out if somebody opened the envelope on its way to the visa officer to tamper the content of the envelope. Hope this helps.
Thank you.