Could be due to limited/full-range RGB mismatch. Make sure your TV is in PC mode.
And just to note, if your TV is in limited range mode, the image will be brighter, but blown out and crushing blacks. So in that case the darkened picture is actually the correct one even if it appears duller to you. You should check correct colour/brightness with 240p test suite or equivalent.
|_gat||1 minute||This cookie is installed by Google Universal Analytics to restrain request rate and thus limit the collection of data on high traffic sites.|
|__gads||1 year 24 days||The __gads cookie, set by Google, is stored under DoubleClick domain and tracks the number of times users see an advert, measures the success of the campaign and calculates its revenue. This cookie can only be read from the domain they are set on and will not track any data while browsing through other sites.|
|_ga||2 years||The _ga cookie, installed by Google Analytics, calculates visitor, session and campaign data and also keeps track of site usage for the site's analytics report. The cookie stores information anonymously and assigns a randomly generated number to recognize unique visitors.|
|_gid||1 day||Installed by Google Analytics, _gid cookie stores information on how visitors use a website, while also creating an analytics report of the website's performance. Some of the data that are collected include the number of visitors, their source, and the pages they visit anonymously.|
|IDE||1 year 24 days||Google DoubleClick IDE cookies are used to store information about how the user uses the website to present them with relevant ads and according to the user profile.|
|test_cookie||15 minutes||The test_cookie is set by doubleclick.net and is used to determine if the user's browser supports cookies.|
|wp_woocommerce_session_9cc3598a6315be16da4f85bb374cf6a5||2 days||No description|