Allow colors to be configured via config file #406

Job	Run time
install-cross (linux-musl)	6s
macos (stable, x86_64-apple-darwin)	39s
macos (beta, x86_64-apple-darwin)	48s
macos (nightly, x86_64-apple-darwin)	47s
linux (stable, arm-unknown-linux-gnueabi)	26s
linux (stable, armv7-unknown-linux-gnueabihf)	7s
linux (stable, i686-unknown-linux-musl)	21s
linux (stable, x86_64-unknown-linux-musl)	1s
linux (stable, aarch64-unknown-linux-gnu)	35s
linux (stable, aarch64-unknown-linux-musl)	54s
linux (stable, arm-unknown-linux-gnueabihf)	32s
linux (beta, arm-unknown-linux-gnueabi)	56s
linux (beta, armv7-unknown-linux-gnueabihf)	55s
linux (beta, i686-unknown-linux-musl)	55s
linux (beta, x86_64-unknown-linux-musl)	55s
linux (beta, aarch64-unknown-linux-gnu)	58s
linux (beta, aarch64-unknown-linux-musl)	56s
linux (beta, arm-unknown-linux-gnueabihf)	59s
linux (nightly, arm-unknown-linux-gnueabi)	49s
linux (nightly, armv7-unknown-linux-gnueabihf)	46s
linux (nightly, i686-unknown-linux-musl)	42s
linux (nightly, x86_64-unknown-linux-musl)	55s
linux (nightly, aarch64-unknown-linux-gnu)	55s
linux (nightly, aarch64-unknown-linux-musl)	49s
linux (nightly, arm-unknown-linux-gnueabihf)	40s
	17m 26s

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