Paint Colors

#!usr/local/bin/python3.8
# -*- coding: utf-8 -*import
from _collections import deque

MAIN = ('red', 'yellow', 'blue')
SECONDARY = {
    'orange': ('red', 'yellow'),
    'purple': ('red', 'blue'),
    'green': ('yellow', 'blue'),
}


text = deque(input().split())
colors = []

while True:
    if not text:
        break
    if len(text) > 1:
        first_sub_string = text[0]
        last_sub_string = text[-1]
        word = first_sub_string + last_sub_string
        word_2 = last_sub_string + first_sub_string
        if word in MAIN or word in SECONDARY:
            colors.append(word)
            del text[0]
            del text[-1]
        elif word_2 in MAIN or word_2 in SECONDARY:
            colors.append(word_2)
            del text[0]
            del text[-1]
        else:
            first_sub_string = text.popleft()[:-1]
            last_sub_string = text.pop()[:-1]
            middle = len(text) // 2
            if last_sub_string:
                text.insert(middle, last_sub_string)
            if first_sub_string:
                text.insert(middle + 1, first_sub_string)
    else:
        word = text[0]
        if word in MAIN or word in SECONDARY:
            colors.append(word)
            text.pop()
        else:
            text.pop()

for x in colors:
    if x in SECONDARY:
        main_1 = SECONDARY[x][0]
        main_2 = SECONDARY[x][1]
        if main_1 not in colors or main_2 not in colors:
            colors.remove(x)
print(colors)