How to get a larger frame buffer?

The GIGA Display Board is amazing but requires a large buffer. No minimize flicker I use a 490x480 16 bit display buffer and then copy it to the display with tft.drawRGBBitmap

if I use a larger buffer I get the red MBED error LED after uploading my sketch.

Can I use the external SRAM on the GIGA R1 to increase the size of my frame buffer?

Or since I only need a few simple colors is there an 8 bit color version of tft.drawRGBBitmap?