Age-sensitive colour-colour diagrams. Upper left: Hα-FUV vs. FUV − NUV, lower left: NUV − u vs. FUV − NUV, lower right: NUV − u vs. Hα-FUV. Black filled dots are for regions detected in all bands, red filled triangles are lower limits in Hα-FUV, blue filled triangles upper limits in NUV − u, while the cyan filled square the mean value for the diffuse extended tail. The blue, green, and red filled dots and solid lines indicate the expected colours at different ages (in Myr) for the assumed star formation history for an E(B − V) = 0.0, 0.1, and 0.2, respectively. The green numbers are the ages in Myr for E(B − V) = 0.1.