I'm really not sure on the size, I'm thinking 6-9 months. It should fit a baby with head about 15" around.
With a 4mm needle cast on 65 stitches in color A. Work in garter stitch for 6 rows. Cut thread
With a 5mm needle and color B knit in stockinette stitch until hat measures 11 cm, ending with a WS row.
(K6, K2tog) 8 times, K1 (57 stitches)
(K5, K2tog) 8 times, K1 (49)
(K4, K2tog) 8 times, K1 (41)
(K3, K2tog) 8 times, K1 (33)
(K2, K2tog) 8 times, K1, (25)
(K1, K2tog) 8 times, KI (17)
(K2tog) 8 times, K1 (9)
work 1 row
Cut yarn and thread through remaining 9 stitches. Pull tight and sew up back.
Cast on 57 sts on 4mm needles and yarn A.
Row 1: purl
Break yarn and join in yarn C (a third color, or whatever you would like. I just used the two colours I had used in the hat)
Row 2: K2 *K1 and slip this st back onto left needle, lift the next 8 sts on left needle over this stitch and off needle, (yfwd) twice, K first stitch again, K2, rep from * to end.
Row 3: K1 *P2tog, (K1, K1 tbl) into double (yfwd) of previous row, P1, rep from * to last stitch, K1
Row 4: knit
Break yarn and thread through remaining stitches. Pull of tight and fasten off securely. Join row end and edges.
Make another flower using yarn A throughout. Lay this on top of other flower and attach centre of both flowers to hat as in photograph.