I have looked further into my source, which confirms that the 4th, 7th and 9th regiments adopted French-style dress before 1812, the rest hadn't (retaining the czapka and kurtka; specific examples given as the 16th, 8th and 12th, each with distinctive features, particularly to the czapka). Apart from this, the source (Philip Haythornwaite) cautions against general assumptions due to a large number of regimental variations. The same seems to apply to regimental colours.
Haythornwaite gives four different regimental flags: the 2nd line (borne by a volitgeur colour-sergeant), that of the 1st line, the 2nd btn., 13th Line and the 4th btn., 7th line. The first three have a silver eagle flagstaff, that of the 7th line, a simple spear-point. If you want details of the flag for any of these units, I am happy to type up the description. It looks like every btn had some form of colour, though there is quite a variety in size and even the largest is only about 4/5ths the size of a typical French line regiment colour.