They've not "admitted" to anything of the sort. The cameras on board their probes are for scientific purposes first and foremost, so they are designed to extract as much information as possible in particular wavelengths, rather than to take pretty pictures. They're usually (not always, but usually) a monochrome camera that takes multiple images through different colour filters, which are then re-combined back here on earth for the fancy publicity shots. The exact balance of those re-combined colours can vary depending on what they're trying to achieve with the shot and how close they want to bring it to human perceptions of colour, and how much they want to compensate for the different lighting conditions present in such a thin, dusty atmosphere, so sometimes they might be redder, sometimes less so, but that doesn't mean Mars is actually the same colour as the moon in reality. It is red; we can see it's red. Get a telescope and look at it. Up close it tends towards a mixture of reds, oranges, some browns, and even green and blue in places, but the overarching colour of the planet is red.
A lot of the current publicity images of Mars are skewed somewhat away from red to allow more detail to be visible. If they were put into approximately "true colour" (or as close to it as a camera can get), they'd be almost featurelessly red.