I know you said you wanted to use the same tone/shade of each color, but all the traditional designs I can think of include either a lighter color (like the white in ube's quilt) or a darker color (like the medium grey in this 1,000 pyramid quilt I decided to try since Mary Fons came to teach at my guild ... not my thing, by the way. Once I finish this quilt, I'm retreating back to applique, but it was fun learning something new). I'm still cutting those annoying little triangles, but here's a pic of the beginning layout...
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That's a charcoal grey that's reading black & I may trade it out for a medium grey. I have light greys, whites & a pale pink for the triangles that are facing up. You could easily do a pale grey & a pale yellow for the up triangles & a medium blue for the down triangles & you'd have a nice, simple one-block quilt. My sister-in-law coordinated with me about "appropriate" color choices for her posh neighbors. I too was told that I needed to stick with pale colors, but when they saw the picture with the medium greys, they just fell in love with it. Only downside is that all her neighbors who are fighting over who will pay the highest price keep encouraging me to hand quilt it. We'll see how that goes with my nephew's quilt. I'm not sure I'd be willing to do it for non-family... even at the $3,500 offered price tag. Anyways ... just wanted to point out that even people with very particular instructions about colors can be won over when they see what adding one somewhat lighter or somewhat more saturated color can do for the design.