Do you mean flip an image? http://indesignsecrets.com/how-to-flip-or-mirror-an-object-in-indesign.php
To get the colour from the image use the Colour Picker tool - http://indesignsecrets.com/tip-week-color-theme-tool.php
Hardback covers, make sure you allow a 20mm (or more talk to your printers) for bleed, this is what's used to wrap around the cover, and a page is then glued on the inside cover to hold it in place.
There's a few ways - but your printers should be able to provide a template.
The first thing you need to do is establish the trimmed size of the, presumably, loose jacket.
The depth will be 210mm plus 3mm to the top and bottom for bleed (6mm).
The width will be 148 x 2 plus bleed of 3mm each end (6mm) plus an amount for the flaps say 60mm x 2. Plus, and this is where it get's tricky, the spine width. This will depend on the thickness of the case and the number and bulk of the pages.You printer should be able to advise you on this measurement.
You just flip your pic (right to left) for your placed photo (Object > Transform > Flip Horizontal) For the grey thing, draw an oblong to the size you want and fill it will the colour of your choice from the swatch (you can elect the particular grey or dial it in using the Swatch Options panel).
Thanks so much Derek, and for your swift reply. Much appreciated!
See this link also
Be aware you'll need more bleed for a hard back cover - where you should not place any artwork that should be visible, you may have a background image or colour, but if it's not pertinent then it can go into the bleed area which wraps the cover.
Any text or images that require to remain visible, make sure they are well in from the page edge (say at least 8 mm)
It's very important to speak to the printers before commencing.