It is okay to combine smaller bricks to make the size you need.  For example, if you need a 1x4 brick, you can use two 1x2 bricks.

It is also okay to use a different color.

If you want to build each design without keeping any models and don't care what color bricks you use, the minimum set of bricks you need is:

20	— 1x1
23	— 1x2
11	— 1x3
8	— 1x4
7	— 1x6
5	— 1x8

If you want to keep all 20 of the designs without taking them apart, you will need the following bricks:

Black 58 — 1x1 34 — 1x2 7 — 1x3 5 — 1x4 2 — 1x6 2 — 1x8	Blue 26 — 1x1 24 — 1x2 17 — 1x3 8 — 1x4 5 — 1x6 7 — 1x8	Brown 16 — 1x2 5 — 1x3 5 — 1x4 8 — 1x6
Green 9 — 1x1 13 — 1x2 9 — 1x3 7 — 1x4 1 — 1x6 3 — 1x8	Orange 2 — 1x1 7 — 1x2	Red 13 — 1x1 23 — 1x2 10 — 1x3 9 — 1x4 10 — 1x6 7 — 1x8
Tan 8 — 1x2	White 32 — 1x1 20 — 1x2 9 — 1x3 13 — 1x4 10 — 1x6 4 — 1x8	Yellow 15 — 1x1 10 — 1x2 7 — 1x3 8 — 1x4 3 — 1x6

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