The simplest way would be to spawn 3 different headers, one for each group type, and use a visibility conditional on each one so that it was only shown in the desired group type.
For example:
Code:
local party = oUF:SpawnHeader("oUF_MyLayout_Party", nil,
"custom [nogroup][group:party,@party1,noexists][group:raid,@raid6,exists]hide;show")
local raid10 = oUF:SpawnHeader("oUF_MyLayout_Raid10", nil,
"custom [nogroup][group:party][@raid6,noexists][@raid11,exists]hide;show")
local raid25 = oUF:SpawnHeader("oUF_MyLayout_Raid25", nil,
"custom [nogroup][group:party][@raid11,noexists]hide;show")