CSS

sideways linear gradient

/* A gradient tilted 45 degrees,
   starting blue and finishing red */
linear-gradient(45deg, blue, red);

/* A gradient going from the bottom right to the top left corner,
   starting blue and finishing red */
linear-gradient(to left top, blue, red);

/* Color stop: A gradient going from the bottom to top,
   starting blue, turning green at 40% of its length,
   and finishing red */
linear-gradient(0deg, blue, green 40%, red);

/* Color hint: A gradient going from the left to right, 
   starting red, getting to the midpoint color 
   10% of the way across the length of the gradient, 
   taking the rest of the 90% of the length to change to blue */ 
linear-gradient(.25turn, red, 10%, blue);

/* Multi-position color stop: A gradient tilted 45 degrees, 
   with a red bottom-left half and a blue top-right half, 
   with a hard line where the gradient changes from red to blue */
linear-gradient(45deg, red 0 50%, blue 50% 100%);