Drawing Colorful Flowers

Create a new document, fill background with black color

Create a new layer, use Pen tool to make lines like the picture below:

Press Ctrl+Enter to make selection then fill it with white color

Create a new layer, use Pen tool to make other lines, Ctrl+Enter to make selection then fill it with white color

Merge 2 layers then fill it with color #820000

Create a new layer, Ctrl+Click on petal layer to get selection

Choose Gradient to and set properties like this:

Click to enlarge

Apply gradient to selection to get the result like this:

Hit "M" key, use down arrow key to move the selection down 1px then hit Delete key, you will get:

Repeat above step (create new layer, ctrl+click to get selection, fill Gradient), keep selection and hit M key, move the selection like the picture below:

Hit Delete key, change blend mode to Overlay or Softlight, you will get:

Continue to repeat above steps, you will have:

Repeat 2 or 3 times with different distances

Now you will use above steps to makeup for right part

Use Eraser tool to remove redundant parts on your document

It should now look like this

Merge all layers, duplicate petal layer then arrange petals like this

Continue merge 4 petal layers, duplicate this layer 2 times then arrange like this:

You can add some other details you like.

Now you will adjust the color (Ctrl+U) and use some blend modes (Overlay or Softlight) to make some different results

These are my final results