UAS regulatory sequences are fused upstream of the "Brainbow1.1" cassette from Addgene plasmid 18722. The cassette contains open reading frames (ORFs) for 4 fluorescent proteins: Kusabira-Orange, mCherry, EYFP and mCer, with each ORF followed by an SV40 polyadenylation signal. The last three ORFs are tagged with a dual Tag:MyrPalm(mLyn) sequence to target them to the plasma membrane. Three mutually exclusive lox cassettes (loxN, lox2272 and loxP variants) are present. It was expected that in the absence of P1cre recombinase, only Kusabira-Orange (the ORF adjacent to the UAS sequences) would be expressed in the presence of a GAL4 driver, while the addition of P1cre recombinase would result in stochastic removal of one of the lox cassettes, removing the Kusabira-Orange ORF and resulting in GAL4-dependent expression of one of mCherry, EYFP or mCer. However, it was found that both Kusabira-Orange and mCherry (the 1st and 2nd ORFs) are co-expressed from the P{UAS-Brainbow1.1-M.Omni} construct in the absence of P1cre activity in transgenic flies. Despite the default co-expression of Kusabira-Orange and mCherry, the three possible colours that result from excision of a lox cassette (mCherry without Kusabira-Orange, EYFP or mCer) are clearly separable from each other. Increasing the copy number of the P{UAS-Brainbow1.1-M.Omni} construct to two results in six possible colours after excision of a lox cassette.