Goldendoodles
While Golden Retrievers are... golden (technically they can range from near-white to an almost reddish tint), Poodles can come in a much wider array of colors and marking. Add in the mixing of the breeds, and especially when backcrossing back to Poodles of potentially different colors, and the options are even greater.
Goldendoodles primarily follow the coloring options of Poodles and can be a solid color, have one primary color with small spots of another, or have multiple colors. Common colors are black, cream, gold, apricot, red, white, silver, gray, and brown. Puppies from the same littler can potentially have a variety of combinations of both colors and locations of the markings.
Aussiedoodles
Australian Shepherds have 4 recognized colors: Black, Red, Blue Merle, and Red Merle, but can have variations within them including mixes of white and/or brown and can be bi-color or tri-color. Like Goldendoodles, mixing them with Poodles opens even more color combinations. Note that when looking at purebred Australian Shepherds you want to avoid yellow and especially all white coloring, which tends to result in health issues.
In addition to a variety of colors and markings, there are a few specific markings and/or color combinations that are especially unique:
Merle - Merle is a genetic pattern that can be in a dog's coat. Merle comes in different colors and patterns and can affect all coat colors. The merle gene creates mottled patches of color in a solid or piebald coat, blue or odd-colored eyes, and can affect skin pigment as well. The merle pattern is more specific to Aussiedoodles than Goldendoodles and is very rare as it's a recessive gene and two merle's should not be bred together else it can result in health issues.
Parti - Stands for partial (pronounced like party); these consist of two colors, white and another, and the white must cover at least 50% of the body. The most common secondary colors are black, brown, red, and apricot, but it's not restricted to those. There are no requirements for where the colors are located on the body, making each one unique.
Phantom - These are similar to Parti in that there are two colors, but unique in the color combinations and where the markings exist. The Phantom coloring consists of a solid background with patches of another color in specific locations including above the eyes, on the sides of the muzzle, across the chest, down the legs, and under the tail. The Phantom coloring can also be categorized by the color combinations:
Black Phantom - Black with apricot, red, cream, gray, brown, or silver
Chocolate Phantom - Brown background with apricot
Red Phantom - Red background with apricot
Silver Phantom - Silver background with cream
Tuxedo - Similar to Phantom, these are specific color combinations in specific locations. The background coat is most often black, but not required (other colors are very rare). The secondary coat is white and appears in the following locations:
A white bib - Color on the chest that may wrap all the way around the neck
A white belly - This "should" touch the bib, making a continuous white area, and extend down from the belly to the front and hind legs