Purple Gnu in dreams
A wildebeest of the great migrations — the individual absorbed into a moving mass.
How purple changes the reading
Purple colour places the symbol between hot and cool — a reading that has both calm and intensity at once. The dream often uses purple for symbols that do not fit the usual categories cleanly. Take the reading more seriously than you would otherwise; the colour is asking you to.
The base reading of Gnu
A gnu in a dream is the dream's image of life inside the great migration. Wildebeest cross rivers and plains in herds so large that the individual is functionally invisible; the dream brings the animal when you have, for a season, set aside your own pace to move with a crowd. A gnu in a calm herd is the dream telling you the collective momentum is currently serving you. A gnu drowning in a river crossing is the dream marking that the same momentum will, if you are not careful, take you over an edge the herd does not notice.