The P{UAS-Brainbow.L} construct contains UASt regulatory sequences fused upstream of two FRT cassettes, with each cassette containing open reading frames (ORFs) for two fluorescent proteins. The first cassette contains AcGFP1 in the forward orientation and ECFP in the reverse orientation, and the second cassette contains mKO in the forward orientation and EYFP in the reverse orientation. This structure allows stochastic expression of multiple fluorescent proteins from a single P{UAS-Brainbow.L} transgene using FLP mediated excision. In the absence of FLP recombinase the ORF adjacent to the UASt sequence, AcGFP1, is expressed. When FLP is present either of the two distinct FRT cassettes in the P{UAS-Brainbow.L} construct can be irreversibly excised and/or inverted. Depending on which cassette is excised/inverted, any one of the downstream ORFs can become juxtaposed with the UASt sequence, resulting in expression of that protein.