Indeed, I would not trust Herbert Knötel, nor Lienhard and Humbert – Vernet – the above source printed a lot of versions of an identical template coloured in a veriation of schemes, for more see Guy Dempsey's : Napoleon's Army 1807 – 1814.
about the Tirailleurs – Grenadiers – according to an imperial decret 10th of Mai, 1809
Le shako sera surmonté d'un plument rouge pour les tirailleurs – grenadiers
signed by Napoléon himself
then we have the conscrits – grenadiers – which later in 1810 become 3e and 4e régiments de tirailleurs – in 1809 their plume was – red.
And the
Flanqueur – grenadiers which were formed in 1811 – they had no plume.
Weiland (contemporary source) shows and officer of the Tirailleur grenadiers with an entirely red plume
However :
In an article in Uniformes Nr. 88 / 1985 – Rousselot (secondary source) offers the option of the two coloured plumes.
His aruments, according to le tableau général des dépenses in 1809 – they alos got pompoms, which according to Marco de St. Hilaires work about the Guard (secondary source) was red over white for the first regiment and the other way round for the second.
Now when the plume was worn, the pom poms weren't that is either shako with plumes or shako with pom poms.
Rousselot seems to extrapolate from the pompoms – to the plumes and therefore – surprise surprise offers a
red over white plume for the first regiment
and a
white over red plume for the second regiment.
Now that leaves the question ot what colours did they later regiments – 3 and 4 did wear, they should have had red plumes (at least according to regulations).
Hopefully this is not too confusing.
Conclusion : Vernet shows this two coloured plume, for a Tirailleur (Grenadier) – and for a Grenadier Conscrits Tirailleur entirely red.
Weiland shows entirely red for an officer of the Tirailleur Grenadiers.
The imperial decret says red.
So God wills it – it will be your choice in the end ;-)).