how to fix the display colour??

Seems Pioneer thought they were designing a disco light show.

Have you tried the various settings documented on pages 31 and 32: https://www.pioneer.com.au/wp-content/uploads/2019/06/DEH-S5250BT-Operation-Guide.pdf

Last night I stumbled across how to do it when stepping through the various menus... Found one on Illumination and managed to make the thing stop thinking its a disco and STAY on a reasonable colour that is easy to see in the quite bright interior of the motor home.

I had not explored the Internet for a better handbook on this unit so am very grateful that you, GTC, had found and listed its above...far better info than is supplied with the unit.

I need to read up more on how to correctly Manually tune the thing as left to its own devices it locks onto 6 quite strong AM band stations and the you have to fight it to be able to locate and tune in stations that I want in the memory.
Also for prowling around the shortwave bands manual tuning is the only way but how to do that is not really covered in the bare bones scraps of info that are supplied.

Back in the days when I lived in Tamworth I'd do a bit of radio station hunting at night with my HMV radiogram, with a 20m aerial out the window and flung over the roof. I'd pick up Sydney, Melbourne and Brisbane no worries, not all stations of course, due to overlapping frequencies but if there was a clear space the station would come in.

Car radios are generally renowned for being able to pick up AM quite well. However the Japanese, generally speaking, regard AM as inferior, almost spiritually so, so in some cases they go to very little effort to make their radios suck it in. In the two cars I have had in the last twenty years, both Commodore wagons, the radios have picked up AM well. Even in the daytime, I can pick up Sydney stations (just) at Lithgow. The 1994 car had a Eurovox and the 2003 one, which I have at the moment was fitted with a Blaupunkt. It's been a few years since Holdens had Astors in them.

I have honestly never seen a car radio with shortwave bands. They must be a rare beast.

About 40 years ago I had a Ford Pinto. Awful car, but it did have a very good AM radio. No FM.

This Pioneer radio IS quite good for AM reception as I found out over the past few days camped out about 25kms East of York at a delightful spot.
720 6WF from Perth about 110kms away over the Darling range was reasonable reception but 6WA Wagin on 558 romped in with a good clear signal which is about 180kms as the crow would fly.
6DL Dalwallinu on 531 was on a par with 6WF and Dalwallinu was about 200kms to the north but only runs on 10Kw whereas 720 & 558 are both 50Kw transmitters.
All the motor home has for an antenna is short rubber ducky sitting type up on the side wall almost at the top so a bigger antenna would certainly help. (motor home is fibreglass).

Have not been able to reliably manually tune this thing all the way across the AM band at night looking for distant stations...the manual tuning seems a bit clunky as compared to the Schneider which has now gone in the bin.

The display on the Pioneer is superb being bright and VERY clear...the Schneider was hopeless being a LCD type which was unreadable in bright light.

The USB function works very well as does the CD player so VERY pleased with this purchase and am now eying up the original vehicle radio being a Panasonic which again is LCD and impossible to read the display from the drivers seat and the clock in it gains time.

If the Pioneers are still available at the $158 price I can see the Panasonic being hoiked out and replaced as its only a Cassette type and I now have very few cassettes to use in it and the Bluetooth pairing to a mobile phone works very well on the Pioneer and you end up with a hands free setup.

Need to check out the dash slot that the Panasonic occupies and see iF it is compatible with the Pioneer mounting sleeve/bracket as I do not think the Din mounting now used was around when the Dyna was made in 1990.