It seems that SetColorTexture respects any SetGradient in place but SetVertexColor overrides SetGradient. Since SetColorTexture is set to pure white by default we just need to use SetVertexColor to set the average of the gradient. Untested code:
Lua Code:
hooksecurefunc("DefaultCompactUnitFrameSetup", function(frame)
frame.myHealPrediction:SetVertexColor(19/510, 229/510, 177/510)
frame.otherHealPrediction:SetVertexColor(32/510, 142/510, 115/510)
end)
hooksecurefunc("DefaultCompactMiniFrameSetup", function(frame)
frame.myHealPrediction:SetVertexColor(19/510, 229/510, 177/510)
frame.otherHealPrediction:SetVertexColor(5/510, 5173/510, 23/510)
end)