Is Krsna Saguna or Nirguna?

Whether or not Krsna is saguna or nirguna would depend on what one means by the term guna. Does guna mean simply “attribute” or (the more specific) “evolute of primal matter (prakrti)?” On that would depend the answer. In the Bhagavata, the term nirguna, as applied to the Lord, seems to refer to the more specific sense of the word guna. Therefore, in this sense, Krsna is nirguna. He is beyond the influence of the three gunas of primal matter. His body is not gunamaya, composed out of matter; it is purely spiritual in its nature; it is often termed brahmamaya. Also, unlike the jiva—who is, by the way, of the same essential nature as the Lord—there can be no material limitations (upadhi) associated with the Lord.
However, if we speak of nirguna holding in mind the sense of guna as mere “attribute” or “property,” then Krsna is saguna. There is, in this sense, no end to the gunas of Krsna. The Lord is of infinite glories and attributes.