You should never end up with a cut panel in a position such as this - the only place you can hide/protect a cut edge is at the very top of the unit where it can be hidden beneath a cornice moulding. A cut rawe MDF panel like that above an oven or microwave door will get grubby quite quickly and will swell up in a few years. Oven units are often installed above worktop height, but I see yours is in a non-standard position, at the top drawer height, which explains the lack of a suitable off the shelf infill panel. That means that @opps solution of making up your own panel and getting a can of matched auto spray (about £14 to 16 round here) is the only way you'll get what you need, however, I'd still be concerned about that panel directly above the microwave suffering from heat and damp over time unless some form of heat protector were fitted - or that panel were replaced with a (bespoke) stainless steel infill panel
