Rule 107.4a states what the symbols are defined as and rule 612.1 states that symbols can be changed too.107.4a There are five primary colored mana symbols: {W} is white, {U} blue, {B} black, {R} red, and {G} green. These symbols are used to represent colored mana, and also to represent colored mana in costs. Colored mana in costs can be paid only with the appropriate color of mana. See rule 202, “Mana Cost and Color.”
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612. Text-Changing Effects612.1. Some continuous effects change an object’s text. This can apply to any words or symbols printed on that object, but generally affects only that object’s rules text (which appears in its text box) and/or the text that appears in its type line. Such an effect is a text-changing effect. 612.2. A text-changing effect changes only those words that are used in the correct way (for example, a Magic color word being used as a color word, a land type word used as a land type, or a creature type word used as a creature type). An effect that changes a color word or a subtype can’t change a card name, even if that name contains a word or a series of letters that is the same as a Magic color word, basic land type, or creature type.
Added to the sideboard, because they're 35 dollar cards I excluded them but they would be a great addition for the deck.