Being a uniform and flag design service to wargamers and to the imaginary crowned heads of 17th and 18th Century Europe, especially of the Seven Years War period - now By Appointment to the Court of Saxe-Bearstein! (But please note that the uniforms and flags presented here are not fictional - they are genuine 17th and 18th Century uniforms and flags that are as authentic as I can make them from my sources.)
I was asked in the comments on the previous flag if I had any ideas for a speculative Colonel's flag and yes, I have. Here it is, based on the style of many Dutch flags where the Colonel's flag is largely a version of the regimental flag with a white background. I have also added the coat of arms of the province of Holland, as the provincial coat of arms is a common feature on Dutch flags and it livens up the plain white background of this flag.
Back to the Seven Years War again with another set of colours inspired by the Napier illustration from the JSAHR article from Vol. 9, No. 38 (OCTOBER, 1930), p. 243. Good to depict a regiment without a blue regimental colour!.
Again, no point re-inventing the wheel with a long text as there is the detailed Kronoskaf page on the regiment here with uniform details too: https://www.kronoskaf.com/syw/index.php?title=27th_Foot