This page has some background information on bean seed fly from the literature.
Potentially there are two species in the UK - Delia platura and Delia florilega - but they appear to have almost identical development times (1).
The table below shows the estimated durations of the different development stages in days based on information from several sources that is summarised in the paper by Throne & Eckenrode (1). In some cases the estimates vary quite a lot between the different studies. The estimates here are based on converting the develeopment times to 'rates', fitting a linear equation (between 5 and 25°C) and then using the fitted line to estimate development times.
Bean seed fly (Delia platura) - estimated development times at temperatures between 10 and 25°C.
(1) Development Rates for the Seed Maggots Delia platura and D. florilega (Diptera: Anthomyiidae). James E. Throne C. J. Eckenrode. Environmental Entomology, Volume 15, Issue 5, 1 October 1986, Pages 1022–1027.
In terms of trap colour then two studies indicate that blue and white traps are more effective than yellow traps:
Libby, J.L., Chapman, R.K., and Wyman, J.A. (1975). Aspects of cabbage maggot management in Wisconsin. Proceedings of the North Central Branch of the Entomological Society of America 30: 77–78.
Vernon, R.S. and Broatch, J.S. (1996). Responsiveness of Delia spp. (Diptera: Anthomyiidae) to colored sticky traps in flowering and rosette stage canola. The Canadian Entomologist 128, 1077-1085.