When on operations, especially ashore, it is not uncommon for Royal Navy personnel to wear MTP combat uniforms. Those wearing these uniforms obviously wish to make it clear that they are members of the RN and not the army. Most RN combat uniforms will have ‘Royal Navy’ shoulder titles sewn to the top of the sleeves, however the wearing of white ensign patches on the sleeve is also popular. Obviously a large white, red and blue patch would not be appropriate on a camouflage uniform so subdued patches are used instead:
Here then are two variants, one which uses green in place of the red and another that uses brown, the white is replaced with a sand colour in both:
As combat uniforms need to be washed regularly, these patches are designed to use velcro to allow them to be taken on and off easily. Each of the patches has the hook side of the velcro attached to the back, and a suitably sized piece of loop fabric is provided that can be sewn to the sleeve:
As well as being helpful for washing, having the insignia easily detached can help with operational security when it is necessary to disguise the units of particular personnel- it is very easy to just pull these ensigns off and put them in a pocket.
I am unsure if these patches are actually issued by the RN, or are privately purchased by individuals wishing to make it clear their service.