When it comes to describing the shade of red and yellow, there are plenty of options available. Some of the synonyms for the phrase "most red-yellow" include fiery, vibrant, bold, intense, and radiant. Other possible options include blazing, brilliant, deep, rich, and warm. Depending on the context in which the phrase is used, different synonyms may be chosen to convey different shades of the color. For example, "radiant" may be used to describe a bright, sunny day, while "deep" might be used to describe the color of autumn leaves. Ultimately, when choosing a synonym for "most red-yellow," it's important to consider the overall tone and mood that is being conveyed.