More common with Maltipoos is the parti-colored coat as opposed to the solid. If the dog has more than 50% black and any other secondary color, he will be a black-parti. Therefore, the second color may be anywhere from 1 to 49%. However, with this said, normally if the second color is 10% or less, it would be termed a 'mismark' and therefore the Maltipoo would be a black mis-mark.
Just about any other color may accompany black. Common are red, tan and brown
The Sunburning Effect
Black coats, if exposed to too much sunlight can develop red tinting over a period of time. This is often referred to as sunburning although it does not affect the skin in any way. While the previously black hairs that end up having red highlights may still be in good condition, it is not uncommon for them to be a bit dried out.
If you have a black Maltipoo and want him to retain his coloring, you will want to use a quality leave-in spray each day. This will add a thin layer of protection to the hair strands for when you take him out for walks, bathroom trips and whatnot. It is important to remember that one day out in the sun will not affect a black coat... It is day after day... adding up to months and years that can add reds and lighter highlights.
Therefore, getting into a daily routine of using your leave-in product will ensure that you can let your Maltipoo enjoy the outdoors without any concerns that it will end up changing his beautiful black color.