Generate Randomized Color Board

generate a random (height x width) grid such that for every coordinate (i, j), there can be no three consecutive same colors in a row or in a column.

generate(int: width, int: height, list: colors)

Example:

getvalidMatrix(3, 3, [0, 1, 2])

output:

[

[1, 2, 1],

[1, 0, 2],

[0, 1, 2],

]

import random
def getvalidMatrix(length,width,colors):
    map = dict()
    
    for i in range(len(colors)):
        map[colors[i]]=i
        
    res = [[0] * length] * width
    for i in range(length):
        for j in range(width):
            end = len(colors)
            if i - 1 >= 0 and i - 2 >= 0 and res[i-1][j] == res[i-2][j]:
                index = map[res[i-1][j]]
                colors[index] = colors[end]
                colors[end] = map[res[i-1]][j]
                end -= 1
            if j - 1 >= 0 and j - 2 >= 0 and res[i][j-1] == res[i][j-2]:
                index = map[res[i][j-1]]
                colors[index] = colors[end]
                colors[end] = map[res[i][j-1]]
                end -= 1
            next=random.randint(0,end)
            res[i][j] = colors[next]
            
    return res

if __name__ == '__main__':
    length = 3
    width = 3
    colors = [0,1,2]
    print(getvalidMatrix(length, width, colors))

I got IndexError: list index out of range with the code above. Which part of the code should I fix in order to avoid the IndexError?