The first time I heard about the split the reasons mentioned were something about party politics (communism and non-communists positions). Later on, I heard about a crucial problem, how to get organized. It seems some wimmin were into more conventional ways of getting organized. Considering I'm quite happy with organizational modes which respect not bossing people around, I was happy at Blue Gate, so I never really managed to get myself interested in the issue of the split.
From the online archives I found, it seems the split happened in 1987, this is, before this period this project is devoted to:
'Greenham Women Everywhere' newsletter (1 edition), 1987, created by women at Orange and Violet Gates following a dispute with Yellow Gate. Newsletters produced by GCW 5GCW/D/1 1985-1998.
King's Cross Women's Centre 5GCW/G c.1986-1991: Correspondence, leaflets and press clippings concerning relationship between Yellow Gate Camp and King's Cross Women's Centre. Includes information on the 1987 split between Yellow Gate and the other peace camps at Greenham - this included one accusation relating to racism.
Source: National Archives. United Kingdom, at this web address