Blue pumpkins

Jarrahdale Pumpkin

Photo: Pixabay

Heirloom. Blue and grey. Medium to big. Deeply ribbed. Flattened and somewhat blocky. Orange flesh. Great for roasting and decorating.
Available in the Fall.
You can buy seeds on Amazon.

Crown Prince Squash

Medium to big. Flattened.With bluish or greyish moderately ribbed skin and orange flesh. The rind can be smooth or covered with spots and small bumps. This squash is hard to carve because of its thick flesh. It's perfect for cooking, canning, and baking.

Available in the Fall.

You can buy seeds on Amazon.

Nanticoke Squash

Photo:
Experimental Farm Work

North American heirloom. Its name comes from Nanticoke People that inhabited the Chesapeake Bay and Delaware (amongst others). 
It's available in a variety of colors (blue, pink, grey, brown, orange, dull-orange, pinkish, white, green, red, few of the above mixed together) and shapes (turban-like, round, round, and slightly flattened, resembling a wheel of cheese,drop-shaped). Some may have warts here and there. They can be cooked, baked, or used as decor pieces.
Seeds available at Experimental Farm Work.

Queensland Blue Pumpkin

Photo: Pixabay

Heirloom. Australian variety. Colors may vary (from deep-blue and green to grey & mildew-blue). It's deeply ribbed. Round or blocky, sometimes turban-shaped. Can grow up to 10lbs. Good for roasting, very sweet. Exceptional decor piece.
Available in the Fall.
You can buy seeds on Amazon.

Thai Kang Kob Pumpkin

Photo: Rareseeds

Medium-sized, flattened, heavily ribbed, covered with warts and bumps.
Deep-yellow to mildew-blue. Turns dull-orange in storage.
Full-flavored orange flesh.
Available in the Fall.
You can buy seeds at Rareseeds.

Tokyo Blue Squash or Tokyo Pumpkin

Photo: Rareseeds

Small to medium, round, or drop-shaped (often resembles a Red Kuri squash).

Green with blue and grey undertones.

It has a sweet-scented, bright-yellow flesh.

Its skin is somewhat rough.

Available in the Fall.

You can buy seeds at Rareseeds.

Yokohama Squash

Photo: Rareseeds

Rare variety. It's flattened, uneven, and deeply ribbed. Imploded at the top. Its skin is rough, blue to deep green with warts and bumps here and there. The flesh is yellow or yellow-orange.
Available in the Fall & Winter.
You can buy seeds on Rareseeds website.

Learn more about different pumpkin types: