[Phanx]

You should avoid doing a GetSpellInfo lookup on every UNIT_AURA event. You can also avoid the cost of the string concatenation by including the color codes directly in your format pattern.

local DANCING_STEEL = GetSpellInfo(120032)
oUF.Tags.Events["GhostSDTime"] = "UNIT_AURA"
oUF.Tags.Methods["GhostDSTime"] = function(u)
    local _, _, _, _, _, _, expirationTime = UnitAura(u, DANCING_STEEL)
    if expirationTime then
        return format("|cff6670ff%.0f|r", expirationTime - GetTime())
    end
end