This is a raglan sleeved, boat neck jumper. The body is built with centre-decrease domino squares set on the diagonal (=diamond), joined as you go. Tweed and Alpaca1 yarns are held together, creating a light structure. Small colour blocks are knit at tip of some diamonds, in two threads of Spinni.

Raglan sleeve top knit with centre decreases, but as single piece. Lower sleeve a separate piece. Everything is fully charted, with schematic.
250g Tweed
150g Alpaca1
10g each of four contrast colours
JPN6 needle