White looks dull?

I just created a simple few lines of code:

While
cls
SetColor(255, 255, 255)
DrawRect(0, 0, 64, 64)
flip
until keyhit(KEY_ESCAPE)

The white looks like grey. Is this something to do with Blitzmax. Is the default Alpha 0.5 or am I missing something else?

No, I bet you have set the Colordepth to 16bit.
In this case BMAX dither (hope its the right word) because the
Color Value you give Bmax is 32bit and BMax doesn't care about
this.
I know that there was a topic about this bug but i cant'find it. In this Topic Marc has described how to calculate the needed color Values. Maybe you search the Forum for this Topic.

Hard to say, but probably not.

On my monitor white looks entirely white, both in 32 and 16 bit display dpepths. Maybe it's a driver issue?

I bet for a low gama setup in your graphic driver

Yep its because its in 16 bit. More info -> D3D7 SetMaskColor bug

What graphics card are you using pangyan?

Odd. On my computer the following produces two entirely indistinguishable rects (in 16-bit obviously, you can see a subtle difference in 32):

Graphics 800,600,16
SetColor 255,255,255
DrawRect 0,0,128,128
SetColor 248,252,248
DrawRect 128,0,128,128
Flip
WaitMouse

Can someone please confirm which graphics card / driver combinations give unreliable results?

the rects are exactly the same for me.