Displaying Pygame Builtin Colors

import pygame
from pygame.sprite import Group, Sprite

class SimpleButton(Sprite):
    def __init__(self, font, text, rect, callback, foreground, background, midground):
        Sprite.__init__(self)

        self.font = font
        self.rect = rect
        self.hover = False
        self.callback = callback
        self.midground = midground
        self.foreground = foreground
        self.background = background
        self.image = pygame.Surface(self.rect.size)
        self.text(text)

    def text(self, text):
        self.text_image = self.font.render(text, 1, self.foreground)
        self.update_image()

    def on_mousemotion(self, event):
        hover = self.rect.collidepoint(event.pos)
        if self.hover != hover:
            self.hover = hover
            self.update_image()

    def on_mousebuttonup(self, event):
        if event.button == 1:
            if self.hover:
                self.callback(self)

    def update_image(self):
        if self.hover:
            self.image.fill(self.midground)
        else:
            self.image.fill(self.background)

        rect = self.image.get_rect()
        text_rect = self.text_image.get_rect()
        text_rect.center = rect.center
        self.image.blit(self.text_image, text_rect)

class TextBlock(Sprite):
    def __init__(self, font, text, rect):
        Sprite.__init__(self)

        self.font = font
        self.rect = rect
        self.image = pygame.Surface(self.rect.size)
        self.text(text)

    def colors(self, text):
        if text:
            bg = self.background = pygame.Color(text)
            if bg.r < 128 and bg.g < 128:
                self.foreground = pygame.Color('white')
            else:
                self.foreground = pygame.Color('Black')
        else:
            self.background = pygame.Color('Black')

    def text(self, text):
        self.colors(text)
        self.image.fill(self.background)

        if text:
            text_image = self.font.render(text, 1, self.foreground)

            rect = self.image.get_rect()
            text_rect = text_image.get_rect()
            text_rect.center = rect.center
            self.image.blit(text_image, text_rect)

class ColorState:
    def __init__(self):
        # color keys
        self.keys = pygame.color.THECOLORS.keys()
        for color in ("gray", "grey"):
            self.keys = [k for k in self.keys if color not in k]

        self.keys.sort()
        self.position = 0
        self.sprites = Group()
        self.buttons = Group()
        self.blocks = Group()
        self.font = pygame.font.Font(None, 24)

        for x in range(5):
            for y in range(10):
                pos = x * 10 + y
                rect = pygame.Rect(25 + x * 150, 10 + y * 50, 140, 40)
                block = TextBlock(self.font, self.keys[pos], rect)
                block.add(self.sprites, self.blocks)

        colors = pygame.Color("White"), pygame.Color("Navy"), pygame.Color("Dodgerblue")
        rect = pygame.Rect(405, 550, 100, 40)
        button = SimpleButton(self.font, ">>", rect, self.color_forwards, *colors)
        button.add(self.sprites, self.buttons)

        rect = pygame.Rect(295, 550, 100, 40)
        button = SimpleButton(self.font, "<<", rect, self.color_backwards, *colors)
        button.add(self.sprites, self.buttons)

    def color_forwards(self, button):
        length = len(self.keys)
        if self.position + 50 < length:
            self.position += 50

            for enum, sprite in enumerate(self.blocks):
                pos = self.position + enum
                if pos < length:
                    sprite.text(self.keys[pos])
                else:
                    sprite.text(None)

    def color_backwards(self, button):
        if self.position >= 50:
            self.position -= 50
            length = len(self.keys)

            for enum, sprite in enumerate(self.blocks):
                pos = self.position + enum
                if pos < length:
                    sprite.text(self.keys[pos])
                else:
                    sprite.text(None)

    def draw(self, surface):
        self.sprites.draw(surface)

    def event(self, event):
        if event.type == pygame.MOUSEMOTION:
            for sprite in self.buttons:
                sprite.on_mousemotion(event)

        elif event.type == pygame.MOUSEBUTTONUP:
            for sprite in self.buttons:
                sprite.on_mousebuttonup(event)

class ColorMachine:
    def __init__(self):
        # basic pygame setup
        pygame.display.set_caption("Pygame Builtin Colors")
        self.surface = pygame.display.set_mode((800, 600))
        self.rect = self.surface.get_rect()
        self.clock = pygame.time.Clock()

        # State
        self.state = ColorState()

    def mainloop(self):
        running = True
        while running:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    running = False
                else:
                    self.state.event(event)

            self.state.draw(self.surface)
            pygame.display.update()
            self.clock.tick(30)

def main():
    pygame.init()
    machine = ColorMachine()
    machine.mainloop()
    pygame.quit()

main()