This was an initial proposal, with the same colors in a slightly boring horizontal triband:

green-yellow-black-triband

Another proposal rearranged it a bit, but was discarded as too similar to the flag of Tanganyika, which seems quite reasonable, since they did not know that problem would be short-lived:

flag with green-yellow-black-yellow-black horizontal stripes

In the end they went for the saltire, which seems like a great choice, creating a more unique and interesting design.

Wikipedia page about the flag