Custom air brushed paint
This bike was restored by Vintage Mountain Bike Workshop and on display at The Pro's Closet museum for a number of years.
Write up below is directly from Vintage Workshop's website where the bike was restored:
"In 1987 Cannondale's top-of-the-line mountain bike was the SM900, available with the new Suntour XC 9000 index shifting group and a selection of parts from Dia Compe, Sugino, and Sakae. This particular example was owned by a Cannondale employee and features Charlie Cunningham-designed Suntour roller cam brakes and much older Araya 7X rims. The SM900 model was featured prominently in magazine literature in part because of the bold color scheme and the Dupont Imron paint with the option for air-brushed custom graphics. As a signature, the frame painter would mark their initials on the right-side dropout, in this case indicated by the letters "BS." The bikes had decidedly East Coast geometry, with a 13" high bottom bracket to better clear rocks and technical terrain, and enduro-style geometry with a generous 23 inch toptube and short 80 mm stem. The chainstays of the bikes underwent significant manipulation to increase tire and chainring clearance while the seatstays were flattened to increase vertical compliance. The over-sized aluminum tubes were mated to a steel unicrown fork that looks severely under-sized yet performs surprisingly well. It would be a few more years before Cannondale would introduce the Pepperoni aluminum fork to complete the over-sized look. On the trail the bike is well mannered despite some odd proportions, and in many ways illustrates the wide design window a bike manufacturer has to work with in creating a capable bike."