A number of users have asked whether the theme will support the brand guidelines issued in 2018 by The Scout Association. The short answer is yes it will, and work is not only underway but really at the final defluffing stages unless something has been overlooked. The intention is to bring this documentation site up to date and then release the new version (6.0.0), but if you don't want to wait make sure you read to the bottom of the page.
When the new version of the theme appears you may find you have to work through Easy Theme Options resetting your colour choices. The previous brand colours will still be available in the theme to assist in transition, along with the eight new 'Scout' colours for 2018 (and black and white) but it has proved desirable to change the names used for them behind the scenes and this will confuse things.
The new branding guidelines don't include any colours that reflect the current logo and uniform colours, and this provides an additional reason to retain the 2015 colours in the theme, as they include some of the 'missing' ones. The 2018 versions of the Beavers and Cubs logos have changed colour.
In the past, TSA brand guidelines were quite insistent on the logo only appearing in the purple (as it was then). It now seems that they would like groups in the regions to use regional colour logos. Rather unhelpfully these aren't in the distributed logos zip file so the Scout Red, Scout Green and Scout Blue logos have had to be improvised.
It was already possible to add a custom logo to the theme if you use Easy Theme Options. You just need to upload it to the Media Library, resize it to be about 100 pixels wide, note its ID (at the end of the URL) and then go into the Header tab of the Theme Options. There you will see that you can enter the ID of the logo in and adjust the positional offsets. So if you want the new logo in NOW, you can do it. You might find the purple will clash something rotten.
If you consider that the new version of the theme must be pretty stable if it is in use on this site and don't want to wait for the 'official' release, the installation file is available. You'll want to go into Easy Theme Options and do a 'save', to make things work properly, and also fix any colour selections you have.